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Redmine Ruby master - Feature #20054 (Rejected): Replace the use of `def` in endless method definitions w...https://bugs.ruby-lang.org/issues/200542023-12-09T06:21:22Zsawa (Tsuyoshi Sawada)
<p>I propose to remove the use of keyword <code>def</code> from the syntax of endless method definition, and introduce a new sigil instead of it. There are several possibilities for what character to use as the sigil, but the most seemingly promising one to me at this point is the colon. So, instead of:</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="k">def</span> <span class="nf">foo</span> <span class="o">=</span> <span class="n">method_body</span>
</code></pre>
<p>I propose to write</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="ss">:foo</span> <span class="o">=</span> <span class="n">method_body</span>
</code></pre>
<p>There a few reasons to dispense with <code>def</code> in endless method definition.</p>
<p>First, the current syntax for endless method definition looks too similar to conventional method definition. Without endless method definition, we could already define a method in a single line:</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="k">def</span> <span class="nf">foo</span><span class="p">;</span> <span class="n">method_body</span> <span class="k">end</span>
</code></pre>
<p>and compared to this, what the endless method definition does is that, it only saves you from typing the <code>end</code> keyword just by replacing the semicolon with an equal sign. This actually had not made much sense to me. Just saving you from typing the keyword <code>end</code> looks too small of a change for introducing new syntax. In order for endless method definition syntax to be justified (as a shorthand for conventional method definition), it needs to save more typing.</p>
<p>Second, in <a class="issue tracker-1 status-5 priority-4 priority-default closed" title="Bug: Endless method and parsing priorities (Closed)" href="https://bugs.ruby-lang.org/issues/19392">#19392</a>, some people are claiming to change the precedence involving endless method definition. I agree with Matz and other developers who support the current precedence in which:</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="k">def</span> <span class="nf">foo</span> <span class="o">=</span> <span class="n">bar</span> <span class="ow">and</span> <span class="n">baz</span>
</code></pre>
<p>is interpreted as:</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="p">(</span><span class="k">def</span> <span class="nf">foo</span> <span class="o">=</span> <span class="n">bar</span><span class="p">)</span> <span class="ow">and</span> <span class="n">baz</span>
</code></pre>
<p>and I understand that the controversy is due to the look and feel of the keyword <code>def</code>. <code>def</code> has lower precedence than <code>and</code> in conventional method definition, although <code>=</code> has higher precedence than <code>and</code> in variable/constant assignment. Mixing the low-precedence <code>def</code> and the high-precedence <code>=</code> into a single syntax was the cause of the trouble, according to my opinion.</p>
<p>Thence, we should get rid of <code>def</code>. Once we do so, we need to distinguish endless method definition from variable/constant assignment in a new way. What came to my mind was to use a single character: a sigil.</p>
<p>Especially, using the colon seems to make sense to me for several reasons:</p>
<p>Most importantly, assignment to a symbol is impossible, and it currently raises a syntax error, so it would not conflict with variable/constant assignment syntax.</p>
<p>Within Ruby syntax, symbol is naturally used to represent a method name. For example, in <code>foo(&:bar)</code> constructions, users are used to passing a method name as a symbol. Also, a method definition returns a symbol representing the method name. So, making the endless method definition syntax look superficially like an "assignment to a symbol" would make sense.</p> Ruby master - Feature #19889 (Feedback): Let `Kernel.#require` search for files relative to the c...https://bugs.ruby-lang.org/issues/198892023-09-18T13:10:36Zsawa (Tsuyoshi Sawada)
<p>My understanding is that <code>./</code> and <code>../</code> in the given path argument are interpreted relative to:</p>
<p>(1)</p>
<ul>
<li>The current working directory (for <code>load</code> or <code>require</code>)</li>
<li>The requiring file's path (for <code>require_relative</code>)</li>
</ul>
<p>which shows a division of labor between the methods, and seems reasonable. However, when it comes to other relative paths (e.g., <code>foo/bar.rb</code>), they are interpreted relative to:</p>
<p>(2)</p>
<ul>
<li>Paths in <code>$LOAD_PATH</code> (for <code>require</code>)</li>
<li>Paths in <code>$LOAD_PATH</code> or <strong>the current working directory</strong> (for <code>load</code> or <code>require_relative</code>)</li>
</ul>
<p>For example, given:</p>
<ul>
<li>File <code>some_path/foo/a.rb</code>
</li>
<li>File <code>some_path/b.rb</code> with content <code>require "foo/a"</code>
</li>
<li>Current directory at <code>some_path</code>,</li>
</ul>
<p>running <code>ruby b.rb</code> raises a <code>LoadError</code>, but given:</p>
<ul>
<li>File <code>some_path/foo/a.rb</code>
</li>
<li>File <code>some_path/b.rb</code> with content <code> require_relative "foo/a"</code>
</li>
<li>Current directory at <code>some_path</code>,</li>
</ul>
<p>running <code>ruby b.rb</code> does not raise an error.</p>
<p>The search path in (2) for <code>require</code> is a proper subset of that of <code>load</code> and <code>require_relative</code>. There is no division of labor here; there is only inconvenience for <code>require</code>.</p>
<p>Furthermore, in (1), <code>require</code> (as well as <code>load</code>) is concerned with the current working directory while <code>require_relative</code> is not, but in (2), the relation is reversed: <code>require_relative</code> (as well as <code>load</code>) is concerned with the current working directory while <code>require</code> is not.</p>
<p>This situation is making the specification of <code>require</code> versus <code>require_relative</code> difficult to understand, as well as causing inconvenience.</p>
<p><strong>Proposal</strong>: For non-<code>./</code>-or-<code>../</code> relative paths, I propose to let <code>Kernel.#require</code> search relative to the current working directory if the file is not found relative to the paths in <code>$LOAD_PATH</code>, so that the methods <code>load</code>, <code>require</code>, and <code>require_relative</code> all work the same in this respect.</p> Ruby master - Feature #19832 (Rejected): Method#destructive?, UnboundMethod#destructive?https://bugs.ruby-lang.org/issues/198322023-08-06T04:39:36Zsawa (Tsuyoshi Sawada)
<p>I propose to add <code>destructive?</code> property to <code>Method</code> and <code>UnboundMethod</code> instances, which shall behave like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">String</span><span class="p">.</span><span class="nf">instance_method</span><span class="p">(</span><span class="ss">:<<</span><span class="p">).</span><span class="nf">destructive?</span> <span class="c1"># => true</span>
<span class="no">String</span><span class="p">.</span><span class="nf">instance_method</span><span class="p">(:</span><span class="o">+</span><span class="p">).</span><span class="nf">destructive?</span> <span class="c1"># => false</span>
</code></pre>
<p>One main purpose of using these classes is to inspect and make sure how a certain method behaves. Besides arity and owner, whether a method is destructive or not is one important piece of information, but currently, you cannot achieve that from <code>Method</code> or <code>UnboundMethod</code> instances.</p>
<p>The problem is how to implement this. It is best if this information (whether or not a method is destructive) can be extracted automatically from the method definition.</p>
<p>Unlike owner and arity, it may or may not be straightforward by statically analyzing the code. I think that, if a method definition defined at the ruby level does not call a destructive method anywhere within its own definition, and no dynamic method calls (<code>send</code>, <code>eval</code>, etc.) are made, then we can say that the method is non-destructive. If it does call, then the method is most likely a destructive method (it would not be destructive if the internally-called destructive method is applied to a different object. Or, we could rather call that a destructive method in the sense that it has a destructive side effect).</p>
<p>If doing that turns out to be difficult for some or all cases, then a practical approach for the difficult cases is to label the methods as destructive or not, manually. We can perhaps have methods <code>Module#destructive</code> and <code>Module#non_destructive</code> which take (a) symbol/string argument(s) and return the method name(s) in symbol so that they can be used like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span>
<span class="n">destructive</span> <span class="kp">private</span> <span class="k">def</span> <span class="nf">some_destructive_private_method</span>
<span class="o">...</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>or</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span>
<span class="k">def</span> <span class="nf">foo</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">bar</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">baz</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="n">non_destructive</span> <span class="ss">:foo</span><span class="p">,</span> <span class="ss">:baz</span>
<span class="n">destructive</span> <span class="ss">:bar</span>
<span class="k">end</span>
</code></pre>
<p>or</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span>
<span class="n">non_destructive</span>
<span class="k">def</span> <span class="nf">foo</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">baz</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="n">destructive</span>
<span class="k">def</span> <span class="nf">bar</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>When the method is not (yet) specified whether destructive or not, the return value can be <code>"unknown"</code> (or <code>:unknown</code> or <code>nil</code>) by default.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">String</span><span class="p">.</span><span class="nf">instance_method</span><span class="p">(</span><span class="ss">:<<</span><span class="p">).</span><span class="nf">destructive?</span> <span class="c1"># => "unknown"</span>
</code></pre> Ruby master - Feature #19734 (Rejected): Let `Dir` methods be available to `File`https://bugs.ruby-lang.org/issues/197342023-06-17T14:53:51Zsawa (Tsuyoshi Sawada)
<p>I propose to let <code>Dir</code> singleton methods be available to <code>File</code> in some way. Motivations are as follows.</p>
<p>When we want to do something with a file (for example <code>File.read</code> or <code>File.write</code>), we quite often want to achieve the home directory. If we are in the mode of thinking in the ream of <code>File</code>, we would likely come up with <code>File.expand_path("~")</code>. However, this is cumbersome, and actually, <code>Dir.home</code> is simpler. But my experience is that switching the mind to <code>Dir</code> when thinking about <code>File</code> require extra cognitive load.</p>
<p>Also, many methods defined in <code>File</code> work for both a file or a directory. When we are doing something with a directory, we have to stop and think whether the method we want to use is defined in <code>File</code> or in <code>Dir</code>. It is possible to do that, but that also requires extra cognitive load.</p>
<p>I thought things would become simpler if we do not need to switch between these two classes in mind, and keep using <code>File</code>. There are a few singleton methods that are defined on both <code>File</code> and <code>Dir</code>:</p>
<pre><code>delete/unlink, empty?, exist?, new/open
</code></pre>
<p>For them, perhaps some modification can be made.</p> Ruby master - Bug #19733 (Feedback): Kernel#Rational does not accept prefix 0https://bugs.ruby-lang.org/issues/197332023-06-15T00:44:52Zsawa (Tsuyoshi Sawada)
<p><code>Integer</code> and <code>Rational</code> literals accept prefix <code>0</code>. There is no difference in this respect.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mb">0b10</span> <span class="c1"># => 2</span>
<span class="mb">0b10</span><span class="n">r</span> <span class="c1"># => (2/1)</span>
</code></pre>
<p>However, when it comes to <code>Kernel#Integer</code> and <code>Kernel#Rational</code>, the former accepts prefix <code>0</code> while the latter does not. This is confusing. And as I do not see any reason they should behave differently, I think it is a bug.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Integer</span><span class="p">(</span><span class="s2">"0b10"</span><span class="p">)</span> <span class="c1"># => 2</span>
<span class="no">Rational</span><span class="p">(</span><span class="s2">"0b10"</span><span class="p">)</span> <span class="c1"># !> ArgumentError</span>
</code></pre> Ruby master - Feature #19600 (Closed): Method `clamp?`https://bugs.ruby-lang.org/issues/196002023-04-14T12:47:47Zsawa (Tsuyoshi Sawada)
<p>Currently, we have pairs of non-predicate and predicate methods like <code>String#match</code> and <code>String#match?</code>. Along this line, I propose the following. They are brain-friendly, and make programmers happier by saving them from terminology hell.</p>
<ol>
<li>Since by <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: Allow Comparable#clamp(min, max) to accept nil as a specification (Closed)" href="https://bugs.ruby-lang.org/issues/19588">#19588</a>, <code>Comparable#clamp</code>'s behavior is made the same as <code>Range#cover?</code> for range arguments, alias <code>Range#cover?</code> as <code>Range#clamp?</code>.</li>
<li>Synchronize the specification of <code>Comparable#between?</code> with <code>Comparable#clamp</code>, i.e.,<br>
a. Allow <code>Comparable#between?</code> to take a range argument, and<br>
b. Allow <code>Comparable#between?</code> to take <code>nil</code> as either or both of its arguments, or as either or both ends of its range argument.</li>
<li>Alias <code>Comparable#between?</code> as <code>Comparable#clamped?</code>
</li>
</ol> Ruby master - Feature #19559 (Rejected): Introduce `Symbol#+@` and `Symbol#-@`, and eventually re...https://bugs.ruby-lang.org/issues/195592023-03-30T05:23:38Zsawa (Tsuyoshi Sawada)
<p>I propose to define <code>Symbol#+@</code> and <code>Symbol#-@</code>, so that we can add positive or negative polarity to symbols. A possible implementation can be equivalent to what can be achieved by this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Symbol</span>
<span class="k">def</span> <span class="nf">-@</span><span class="p">;</span> <span class="s2">"-</span><span class="si">#{</span><span class="nb">self</span><span class="si">}</span><span class="s2">"</span><span class="p">.</span><span class="nf">to_sym</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">+@</span><span class="p">;</span> <span class="nb">self</span> <span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>The intention behind this is to, eventually, replace boolean positional or keyword arguments with symbols so that, instead of this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"foo"</span><span class="p">.</span><span class="nf">methods</span><span class="p">(</span><span class="kp">false</span><span class="p">)</span>
<span class="nb">gets</span><span class="p">(</span><span class="ss">chomp: </span><span class="kp">true</span><span class="p">)</span>
<span class="no">Integer</span><span class="p">(</span><span class="s2">"2.3"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">false</span><span class="p">)</span>
</code></pre>
<p>we can write like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"foo"</span><span class="p">.</span><span class="nf">methods</span><span class="p">(</span><span class="o">-</span><span class="ss">:inherit</span><span class="p">)</span>
<span class="nb">gets</span><span class="p">(</span><span class="o">+</span><span class="ss">:chomp</span><span class="p">)</span>
<span class="no">Integer</span><span class="p">(</span><span class="s2">"2.3"</span><span class="p">,</span> <span class="o">-</span><span class="ss">:exception</span><span class="p">)</span>
</code></pre> Ruby master - Misc #19111 (Closed): Issues with "feedback" status are tagged as "closedhttps://bugs.ruby-lang.org/issues/191112022-11-08T04:15:18Zsawa (Tsuyoshi Sawada)
<p>I see that the issues under the status "feedback" are tagged as "closed" in the title and in the list. Is this a bug or an intended setting? <a href="https://www.redmineup.com/pages/help/redmine/set-issue-statuses#:~:text=Predefined%20Issue%20statuses%20in%20Redmine,means%20%E2%80%9Copen%E2%80%9D%20issues%20category." class="external">Redmine's document</a> says (bold face mine):</p>
<blockquote>
<p>Predefined Issue statuses in Redmine are New, In progress, Resolved, Feedback, Closed, and Rejected. Statuses marked for Issue closed belong to “closed” issues category; <strong>any other status means “open” issues category</strong>.</p>
</blockquote> Ruby master - Feature #19069 (Rejected): Default value assignment with `Hash.new` in block formhttps://bugs.ruby-lang.org/issues/190692022-10-18T11:58:14Zsawa (Tsuyoshi Sawada)
<p>This is a spin-out from <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Hash.new with non-value objects should be less confusing (Rejected)" href="https://bugs.ruby-lang.org/issues/19063">#19063</a>, and is a recapture of my comment <a href="https://bugs.ruby-lang.org/issues/19063#note-15" class="external">https://bugs.ruby-lang.org/issues/19063#note-15</a>.</p>
<p>I propose to change the behavior of <code>Hash.new</code> when it takes a block with its parameter signature absent. In such case, the evaluated value of the block should be assigned to the hash with the missing key in question (<code>h3</code> below). When the block does take parameters, then the behavior should remain as is now (<code>h1</code>, <code>h2</code> below).</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="n">h1</span> <span class="o">=</span> <span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="n">h</span><span class="p">[</span><span class="n">k</span><span class="p">]</span> <span class="o">=</span> <span class="s2">"foo"</span><span class="p">}</span>
<span class="n">h2</span> <span class="o">=</span> <span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="s2">"foo"</span><span class="p">}</span>
<span class="n">h3</span> <span class="o">=</span> <span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="s2">"foo"</span><span class="p">}</span>
<span class="n">h1</span><span class="p">[</span><span class="ss">:a</span><span class="p">]</span> <span class="c1"># => "foo"</span>
<span class="n">h2</span><span class="p">[</span><span class="ss">:a</span><span class="p">]</span> <span class="c1"># => "foo"</span>
<span class="n">h3</span><span class="p">[</span><span class="ss">:a</span><span class="p">]</span> <span class="c1"># => "foo"</span>
<span class="n">h1</span> <span class="c1"># => {:a=>"foo"}</span>
<span class="n">h2</span> <span class="c1"># => {}</span>
<span class="n">h3</span> <span class="c1"># => {:a=>"foo"}</span>
</code></pre>
<p>This will solve a few problems. First, as discussed in <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Hash.new with non-value objects should be less confusing (Rejected)" href="https://bugs.ruby-lang.org/issues/19063">#19063</a>, many users make the mistake of writing <code>Hash.new([])</code> when they actually mean <code>Hash.new{|h, k| h[k] = []}</code>, and I suspect this is partially due to the fact that the block <code>{|h, k| h[k] = []}</code> is too long, and the users are tempted to avoid writing so. With the proposed feature introduced, the users will be encouraged to naturally write the correct form <code>Hash.new{[]}</code>.</p>
<p>Second, some of the more advanced users than those mentioned above still make the mistake of writing <code>Hash.new{foo}</code> when they actually mean <code>Hash.new{|h, k| h[k] = foo}</code>, and the current proposal is to let them actually be equivalent.</p>
<p>Third, this will resemble a similar construct <code>Array.new(5){[]}</code> and they will make a good parallel.</p>
<p>Indeed, there are situations where the intended behavior is to just run a routine without assigning a new key-value pair to the hash. Examples of current code may be as follows:</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="n">h4</span> <span class="o">=</span> <span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="n">some_routine_to_take_care_of_the_missing_key_situation</span><span class="p">}</span>
<span class="n">h5</span> <span class="o">=</span> <span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="k">raise</span> <span class="no">WrongKeyBlahBlahError</span><span class="p">}</span>
</code></pre>
<p>Such blocks would need to be prepended by a parameter signature <code>|h, k|</code> in order to avoid unwanted results. I do not think such transition would be a huge pain.</p> Ruby master - Bug #18765 (Closed): Wrong description introduced by https://github.com/ruby/ruby/p...https://bugs.ruby-lang.org/issues/187652022-05-09T07:44:14Zsawa (Tsuyoshi Sawada)
<p>Commit <a href="https://github.com/ruby/ruby/pull/4938/files" class="external">https://github.com/ruby/ruby/pull/4938/files</a> introduced problems and made the description wrong.</p>
<ol>
<li>
<p>For methods <code>slice_after</code> and <code>slice_when</code>, it introduces expressions like "partition elements into arrays ('slices')", and for method <code>chunk_while</code>, "partition elements into arrays ('chunks')". It suggests to call the resulting elements using different words depending on the name of the method. But that does not make sense. They are all simply arrays, and there is no need to distinguish a "slice array" from a "chunk array". (They can all be called an "array", "slice", or "chunk", or whatever.)</p>
<p>Perhaps, it is attempting to explain where the method names came from, under the assumption that the words "slice" and "chunk" in these method names are nouns. If so, that is wrong. The succeeding parts "when (block)" and "while (block)" are (to correspond to English) adverbial clauses, not adjectival (relative) clauses; hence, these "slice" and "chunk" must be interpreted as verbs, not nouns. In fact, "a slice when y is not a successor of x" or "a chunk while y is a successor of x" does not make sense, whereas "slice it when y is not a successor of x" and "chunk them while y is a successor of x" do make sense.</p>
<p>The difference between the "slice" and "chunk" methods lies in the process, not the return value. If you want to use these words, it can be something like "slice the receiver into arrays when the block returns a truthy value" and "chunk the elements together while the block returns a truthy value".</p>
</li>
<li>
<p>In the description of <code>slice_when</code> and <code>chunk_while</code>, it says "it calls the block with each element and its successor", but that is not true. If you are going to phrase it that way, then it only calls each element except for the last one.</p>
</li>
<li>
<p>In the description of <code>slice_when</code>, it says "begins a new slice if and only if the block returns a truthy value", but that is not true. Regardless of the value of the block, the first element always begins a new "slice".</p>
</li>
<li>
<p>Most crucially, in the description of <code>chunk_while</code>, the expression "begins a new chunk if and only if the block returns a truthy value" is entirely wrong.</p>
</li>
</ol> Ruby master - Feature #18749 (Rejected): Strangeness of endless inclusive rangeshttps://bugs.ruby-lang.org/issues/187492022-04-22T05:55:59Zsawa (Tsuyoshi Sawada)
<p>I came to think about this while looking at the pull request linked in <a class="issue tracker-1 status-5 priority-4 priority-default closed" title="Bug: Range#cover? returns true for beginless range of different type (Closed)" href="https://bugs.ruby-lang.org/issues/18748">#18748</a>.</p>
<p>Currently, an endless inclusive range covers the corresponding endless exclusive range, but not vice versa:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">(</span><span class="s2">"a"</span><span class="o">..</span><span class="kp">nil</span><span class="p">).</span><span class="nf">cover?</span><span class="p">(</span><span class="s2">"a"</span><span class="o">...</span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#=> true</span>
<span class="p">(</span><span class="s2">"a"</span><span class="o">...</span><span class="kp">nil</span><span class="p">).</span><span class="nf">cover?</span><span class="p">(</span><span class="s2">"a"</span><span class="o">..</span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#=> false</span>
<span class="p">(</span><span class="kp">nil</span><span class="o">..</span><span class="kp">nil</span><span class="p">).</span><span class="nf">cover?</span><span class="p">(</span><span class="kp">nil</span><span class="o">...</span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#=> true</span>
<span class="p">(</span><span class="kp">nil</span><span class="o">...</span><span class="kp">nil</span><span class="p">).</span><span class="nf">cover?</span><span class="p">(</span><span class="kp">nil</span><span class="o">..</span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#=> false</span>
</code></pre>
<p>This looks strange to me. There is not a single element covered by an endless inclusive range that is not covered by the corresponding endless exclusive range. This should mean that there is no difference in coverage between an endless inclusive range and the corresponding endless exclusive range.</p>
<p>However, actually, an interval in mathematics (which I think is the counterpart to Ruby's range) ending in ∞ (which I think is the counterpart to an endless range) is always an open interval (which I think is the counterpart to an exclusive range), and never a closed interval (which I think is the counterpart to an inclusive range).</p>
<p>[a, ∞) is correct.<br>
[a, ∞] is wrong.</p>
<p>From analogy, ideally, endless inclusive ranges should be prohibited in the first place. But that would cause new issues: There is no inclusive-exclusive distinction on the begin side of a range, and that is actually always assumed to be inclusive. Since we have beginless (inclusive) ranges, prohibiting endless inclusive ranges would cause asymmetry.</p>
<p>So what I can think of are the following possibilities (ordered from conservative to radical):</p>
<p>A. Endless inclusive ranges are allowed as is. An endless inclusive range and the corresponding endless exclusive range cover each other.<br>
B. Endless inclusive ranges are disallowed. Beginless (inclusive) ranges are allowed as is.<br>
C. New syntax is introduced in order to describe ranges that are exclusive on the begin side. Inclusive-exclusive distinction can be described on both begin and end sides independently. Endless inclusive ranges and beginless inclusive ranges are disallowed.</p> Ruby master - Feature #18690 (Open): Allow `Kernel#then` to take argumentshttps://bugs.ruby-lang.org/issues/186902022-04-12T09:20:21Zsawa (Tsuyoshi Sawada)
<p><code>Kernel#then</code> passes the receiver to the block as its first positional block parameter.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mf">1.5</span><span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="o">|</span><span class="n">x</span><span class="o">|</span> <span class="no">Math</span><span class="p">.</span><span class="nf">atan</span><span class="p">(</span><span class="n">x</span><span class="p">)}</span>
</code></pre>
<p>I would like to propose to let <code>then</code> take arguments, which would be passed to the block as the other block parameters.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mi">3</span><span class="p">.</span><span class="nf">then</span><span class="p">(</span><span class="mi">4</span><span class="p">){</span><span class="o">|</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="o">|</span> <span class="no">Math</span><span class="p">.</span><span class="nf">hypot</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)}</span>
</code></pre>
<p>There are two uses. First, to separate bulky or repeated parameters from the routine. Instead of writing:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">honyarara</span><span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="o">|</span><span class="n">x</span><span class="o">|</span>
<span class="n">foo</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="n">bar</span><span class="p">(</span><span class="n">fugafugafuga</span><span class="p">)</span>
<span class="n">baz</span><span class="p">(</span><span class="n">hogehogehoge</span><span class="p">)</span>
<span class="n">qux</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">fugafugafuga</span><span class="p">,</span> <span class="n">hogehogehoge</span><span class="p">)</span>
<span class="p">}</span>
</code></pre>
<p>we can then write:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">honyarara</span><span class="p">.</span><span class="nf">then</span><span class="p">(</span><span class="n">fugafugafuga</span><span class="p">,</span> <span class="n">hogehogehoge</span><span class="p">){</span><span class="o">|</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">z</span><span class="o">|</span>
<span class="n">foo</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="n">bar</span><span class="p">(</span><span class="n">y</span><span class="p">)</span>
<span class="n">baz</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="n">qux</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">z</span><span class="p">)</span>
<span class="p">}</span>
</code></pre>
<p>Second, to use a proc with multiple parameters when, for some reason, you do not want to define a method to do it:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">p</span> <span class="o">=</span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">z</span><span class="p">){</span>
<span class="n">foo</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="n">bar</span><span class="p">(</span><span class="n">y</span><span class="p">)</span>
<span class="n">baz</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
<span class="n">qux</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">z</span><span class="p">)</span>
<span class="p">}</span>
<span class="n">honyarara</span><span class="p">.</span><span class="nf">then</span><span class="p">(</span><span class="n">fugafugafuga</span><span class="p">,</span> <span class="n">hogehogehoge</span><span class="p">,</span> <span class="o">&</span><span class="nb">p</span><span class="p">)</span>
</code></pre> Ruby master - Feature #18366 (Rejected): Enumerator#return_evalhttps://bugs.ruby-lang.org/issues/183662021-11-29T04:04:05Zsawa (Tsuyoshi Sawada)
<p>Some <code>Enumerable</code> methods return one or more of the receiver's elements according to the return value of a block it takes. Often, we want such evaluated value rather than the original element.</p>
<p>For example, suppose we want to know the character width sufficient to fit all the strings in an array:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"Hello"</span><span class="p">,</span> <span class="s2">"my"</span><span class="p">,</span> <span class="s2">"name"</span><span class="p">,</span> <span class="s2">"is"</span><span class="p">,</span> <span class="s2">"Ruby"</span><span class="p">]</span>
</code></pre>
<p>We either have to repeat the evaluation of the block:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">max_by</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">).</span><span class="nf">length</span> <span class="c1"># => 5</span>
</code></pre>
<p>or create a temporal array:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">).</span><span class="nf">max</span> <span class="c1"># => 5</span>
</code></pre>
<p>both of which seem not to be optimal.</p>
<p>I propose to have a method <code>Enumerator#return_eval</code> that returns the evaluated value(s) of the block:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">max_by</span><span class="p">.</span><span class="nf">return_eval</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">)</span> <span class="c1"># => 5</span>
<span class="n">a</span><span class="p">.</span><span class="nf">min_by</span><span class="p">.</span><span class="nf">return_eval</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">)</span> <span class="c1"># => 2</span>
<span class="n">a</span><span class="p">.</span><span class="nf">minmax_by</span><span class="p">.</span><span class="nf">return_eval</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">)</span> <span class="c1"># => [2, 5]</span>
<span class="p">[</span><span class="s2">"Ava Davidson"</span><span class="p">,</span> <span class="s2">"Benjamin Anderson"</span><span class="p">,</span> <span class="s2">"Charlie Baker"</span><span class="p">]</span>
<span class="p">.</span><span class="nf">sort_by</span><span class="p">.</span><span class="nf">return_eval</span><span class="p">{</span><span class="n">_1</span><span class="p">.</span><span class="nf">split</span><span class="p">.</span><span class="nf">reverse</span><span class="p">.</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">)}</span> <span class="c1"># => ["Anderson, Benjamin", "Baker, Charlie", "Davidson, Ava"]</span>
</code></pre> Ruby master - Feature #18331 (Open): Kernel.#Timehttps://bugs.ruby-lang.org/issues/183312021-11-13T12:27:30Zsawa (Tsuyoshi Sawada)
<p>I remember that, once, Matz suggested a new literal notation for date/time, but he later withdrew it. It seems like introducing new syntax at this point is less realistic. But I believe that many people have wanted a simple way to create a date/time object.</p>
<p>I propose <code>Kernel.Time</code> or <code>Kernel#Time</code>, in much of the same way as <code>Kernel.#Integer</code>, <code>Kernel.#Float</code>, <code>Kernel.#Complex</code> and others. It should take a string as the first required argument and some optional keyword arguments.</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="no">Time</span><span class="p">(</span><span class="s2">"2021-11-13T21:21:18.027294 +0900"</span><span class="p">)</span> <span class="c1"># => 2021-11-13 21:21:18.027294 +0900</span>
<span class="no">Time</span><span class="p">(</span><span class="s2">"2021-11-13 21:21:18.027294 +0900"</span><span class="p">)</span> <span class="c1"># => 2021-11-13 21:21:18.027294 +0900</span>
<span class="no">Time</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">false</span><span class="p">)</span> <span class="c1"># => nil</span>
</code></pre>
<p>I leave out the specifics. There should be room for debate.</p>
<p>I wish the features nobu implemented in <a href="https://bugs.ruby-lang.org/issues/18033" class="external">https://bugs.ruby-lang.org/issues/18033</a> for <code>Time.new</code> can be carried over to <code>Kernel.#Time</code>.</p> Ruby master - Feature #17773 (Open): Alias `Numeric#zero?` and `Float#zero?` as `Numeric#empty?` ...https://bugs.ruby-lang.org/issues/177732021-04-02T03:49:45Zsawa (Tsuyoshi Sawada)
<p>When dealing with user input fields as in web applications, there are typical values that we want to consider as the default and/or absence of user input. For string/text inputs, list items, and attributes, we have <code>String#empty?</code>, <code>Array#empty?</code>, and <code>Hash#empty?</code> respectively, which seem to correspond to those cases. As for numerics, there are <code>Numeric#zero?</code> and <code>Float#zero?</code>.</p>
<p>However, there is no single term that covers all these cases. In a routine to check through the fields whether there is user input, we have to selectively use <code>empty?</code> or <code>zero?</code> depending on the type of the input field.</p>
<p>Many programming languages other than Ruby typically consider these values as falsy with respect to logical calculation. Ruby handles only <code>nil</code> and <code>false</code> as falsy, and that has clear advantages in many aspects, but with the cost of losing a simple way to handle these default values.</p>
<p>I propose to alias <code>Numeric#zero?</code> as <code>Numeric#empty?</code> and <code>Float#zero?</code> as <code>Float#empty?</code> so that we can simply use <code>empty?</code>. At first, calling zero as empty might sound strange, but at least for non-negative integers, set theoretic definitions usually define zero as the empty set, so it is not that strange after all.</p>
<p>Ruby on Rails' <code>blank?</code> is conceptually similar to this, but <code>0.blank?</code> returns <code>false</code>, so it is a different concept.</p> Ruby master - Feature #17608 (Rejected): Compact and sum in one stephttps://bugs.ruby-lang.org/issues/176082021-02-04T06:18:38Zsawa (Tsuyoshi Sawada)
<p>Many use cases of <code>Array#sum</code> are preceded with the <code>compact</code> method or are followed by a block to ensure the value is addable.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="kp">nil</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">sum</span> <span class="c1"># !> TypeError</span>
<span class="n">a</span><span class="p">.</span><span class="nf">compact</span><span class="p">.</span><span class="nf">sum</span> <span class="c1"># => 6</span>
<span class="n">a</span><span class="p">.</span><span class="nf">sum</span><span class="p">{</span><span class="n">_1</span> <span class="o">||</span> <span class="mi">0</span><span class="p">}</span> <span class="c1"># => 6</span>
</code></pre>
<p>I propose there should be a way to do that in one step. I request either of the following:</p>
<p>A. Change the current behaviour to skip <code>nil</code>s.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">sum</span> <span class="c1"># => 6</span>
</code></pre>
<p>B. <code>Array#filter_sum</code> method</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">filter_sum</span> <span class="c1"># => 6</span>
</code></pre>
<p>C. An option for <code>Array#sum</code></p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">sum</span><span class="p">(</span><span class="ss">compact: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => 6</span>
</code></pre> Ruby master - Feature #17316 (Open): On memoizationhttps://bugs.ruby-lang.org/issues/173162020-11-11T10:22:03Zsawa (Tsuyoshi Sawada)
<p>I have seen so many attempts to memoize a value in the form:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="vi">@foo</span> <span class="o">||=</span> <span class="n">some_heavy_calculation</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
</code></pre>
<p>improperly, i.e., even when the value can potentially be falsy. This practice is wide spread, and since in most cases memoization is about efficiency and it would not be critical if it does not work correctly, people do not seem to care so much about correcting the wrong usage.</p>
<p>In such case, the correct form would be:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">unless</span> <span class="n">instance_variable_defined?</span><span class="p">(</span><span class="ss">:@foo</span><span class="p">)</span>
<span class="vi">@foo</span> <span class="o">=</span> <span class="n">some_heavy_calculation</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
<span class="k">end</span>
</code></pre>
<p>but this looks too long, and perhaps that is keeping people away from using it.</p>
<p>What about allowing <code>Kernel#instance_variable_set</code> to take a block instead of the second argument, in which case the assignment should be done only when the instance variable is not defined?</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">instance_variable_set</span><span class="p">(</span><span class="ss">:@foo</span><span class="p">){</span><span class="n">some_heavy_calculation</span><span class="p">(</span><span class="o">...</span><span class="p">)}</span>
</code></pre>
<p>Or, if that does not look right or seems to depart from the original usage of <code>instance_variable_set</code>, then what about having a new method?</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">memoize</span><span class="p">(</span><span class="ss">:foo</span><span class="p">){</span><span class="n">some_heavy_calculation</span><span class="p">(</span><span class="o">...</span><span class="p">)}</span>
</code></pre> Ruby master - Feature #17290 (Closed): Syntax sugar for boolean keyword argumenthttps://bugs.ruby-lang.org/issues/172902020-10-29T02:54:40Zsawa (Tsuyoshi Sawada)
<p>We frequently use keyword arguments just to pass <code>true</code> value out of the truthy/falsy options given. And in many such cases, the falsy option is set as the default, and only the truthy value is ever passed explicitly. I propose to have a syntax sugar to omit the value of a keyword argument. When omitted, it should be interpreted with value <code>true</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">gets</span><span class="p">(</span><span class="nb">chomp</span><span class="p">:)</span>
<span class="no">CSV</span><span class="p">.</span><span class="nf">parse</span><span class="p">(</span><span class="s2">" foo var "</span><span class="p">,</span> <span class="n">strip</span><span class="p">:)</span>
</code></pre>
<p>should be equivalent to</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">gets</span><span class="p">(</span><span class="ss">chomp: </span><span class="kp">true</span><span class="p">)</span>
<span class="no">CSV</span><span class="p">.</span><span class="nf">parse</span><span class="p">(</span><span class="s2">" foo var "</span><span class="p">,</span> <span class="ss">strip: </span><span class="kp">true</span><span class="p">)</span>
</code></pre>
<p>Additionally, we may also extend this to pragmas.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="c1"># frozen_string_literal:</span>
</code></pre>
<p>to be equivalent to:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="c1"># frozen_string_literal: true</span>
</code></pre> Ruby master - Feature #17177 (Rejected): Include the current file name and the line number in the...https://bugs.ruby-lang.org/issues/171772020-09-18T12:17:57Zsawa (Tsuyoshi Sawada)
<p>In many debugging situations, we want to inspect some objects in more than one source location throughout the code. To be identified where it is called from, it is very common that the method <code>p</code> is used together with a <code>puts</code> method that outputs some marker that distinguishes the location:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">...</span> <span class="c1"># some buggy area or conditional branch</span>
<span class="nb">puts</span> <span class="s2">"== A =="</span>
<span class="nb">p</span> <span class="n">foo</span>
<span class="o">...</span> <span class="c1"># another buggy area or conditional branch</span>
<span class="nb">puts</span> <span class="s2">"== B =="</span>
<span class="nb">p</span> <span class="n">foo</span>
<span class="o">...</span> <span class="c1"># another buggy area or conditional branch</span>
<span class="nb">puts</span> <span class="s2">"bar is:"</span>
<span class="nb">p</span> <span class="n">bar</span>
<span class="o">...</span>
</code></pre>
<p>But this is cumbersome.</p>
<p>Also, after debugging, when we want to remove the <code>p</code> calls from the code, it is sometimes not so trivial to identify where those method calls are written.</p>
<p>I propose that the method <code>p</code> should display not only the objects passed as arguments, but also its source location. Supposing we have a file <code>bar.rb</code> like this,</p>
<pre><code class="rb syntaxhl" data-language="rb"><span class="n">foo</span> <span class="o">=</span> <span class="s2">"a"</span>
<span class="nb">p</span> <span class="n">foo</span>
</code></pre>
<p>running <code>ruby bar.rb</code> should perhaps have an output like this:</p>
<pre><code>At bar.rb:2
"a"
</code></pre>
<p>Then, in a debugging situation like the above, we would only need to write:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">...</span> <span class="c1"># some buggy area or conditional branch</span>
<span class="nb">p</span> <span class="n">foo</span>
<span class="o">...</span> <span class="c1"># another buggy area or conditional branch</span>
<span class="nb">p</span> <span class="n">foo</span>
<span class="o">...</span> <span class="c1"># another buggy area or conditional branch</span>
<span class="nb">p</span> <span class="n">bar</span>
<span class="o">...</span>
</code></pre> Ruby master - Bug #17167 (Closed): Nested numbered parameters are not allowedhttps://bugs.ruby-lang.org/issues/171672020-09-12T15:20:28Zsawa (Tsuyoshi Sawada)
<p>Numbered parameter is allowed in an ordinary block:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">]].</span><span class="nf">each</span><span class="p">{</span><span class="nb">p</span> <span class="n">_1</span><span class="p">}</span>
<span class="c1"># >> [1, 2]</span>
<span class="c1"># >> [3, 4]</span>
</code></pre>
<p>as well as in a nested block:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">]].</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">a</span><span class="o">|</span> <span class="n">a</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="nb">p</span> <span class="n">_1</span><span class="p">}}</span>
<span class="c1"># >> 1</span>
<span class="c1"># >> 2</span>
<span class="c1"># >> 3</span>
<span class="c1"># >> 4</span>
</code></pre>
<p>but not in both at the same time:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">]].</span><span class="nf">each</span><span class="p">{</span><span class="n">_1</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="nb">p</span> <span class="n">_1</span><span class="p">}}</span>
<span class="c1"># >> SyntaxError ((irb):2: numbered parameter is already used in) outer block here</span>
<span class="c1"># >> [[1, 2], [3, 4]].each{_1.each{p _1}}</span>
<span class="o">^~</span>
</code></pre>
<p>I feel that this should be a bug.</p>
<p>Note that an error is not raised when an ordinary block parameter with the same name is used in the outer and the inner blocks:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">]].</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">v</span><span class="o">|</span> <span class="n">v</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">v</span><span class="o">|</span> <span class="nb">p</span> <span class="n">v</span><span class="p">}}</span>
<span class="c1"># >> 1</span>
<span class="c1"># >> 2</span>
<span class="c1"># >> 3</span>
<span class="c1"># >> 4</span>
</code></pre>
<p>If this is not a bug, the specification of numbered parameters is too complex. How am I supposed to use numbered parameters in such use case as above?</p> Ruby master - Feature #17165 (Open): Add `filter` and `flatten` keywords to `Enumerable#map`https://bugs.ruby-lang.org/issues/171652020-09-12T14:46:54Zsawa (Tsuyoshi Sawada)
<p>I had a use case to do <code>map</code> on an enumerable, with 1-level flattening, while skipping <code>nil</code> values.</p>
<p>There are convenient <code>Enumerable#flat_map</code> and <code>Enumerable#filter_map</code> methods, but the problem is that they cannot be used at the same time. I had to chose to do either of the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">array</span>
<span class="p">.</span><span class="nf">filter_map</span> <span class="k">do</span> <span class="o">|</span><span class="n">foo</span><span class="o">|</span>
<span class="n">bar</span> <span class="o">=</span> <span class="n">baz</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="k">next</span> <span class="k">unless</span> <span class="n">bar</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">...</span><span class="p">}</span>
<span class="k">end</span>
<span class="p">.</span><span class="nf">flatten</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
</code></pre>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">array</span>
<span class="p">.</span><span class="nf">flat_map</span> <span class="k">do</span> <span class="o">|</span><span class="n">foo</span><span class="o">|</span>
<span class="n">bar</span> <span class="o">=</span> <span class="n">baz</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="k">next</span> <span class="k">unless</span> <span class="n">bar</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">...</span><span class="p">}</span>
<span class="k">end</span>
<span class="p">.</span><span class="nf">compact</span>
</code></pre>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">array</span>
<span class="p">.</span><span class="nf">flat_map</span> <span class="k">do</span> <span class="o">|</span><span class="n">foo</span><span class="o">|</span>
<span class="n">bar</span> <span class="o">=</span> <span class="n">baz</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="k">next</span> <span class="p">[]</span> <span class="k">unless</span> <span class="n">bar</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">...</span><span class="p">}</span>
<span class="k">end</span>
</code></pre>
<p>The last one of the above may not look so bad, but it requires an extra consideration, and is a bit hacky. When you are in a hurry, it just might not come to your mind.</p>
<p>This led me to realize that <code>flat_map</code> and <code>filter_map</code> should not be independent operations, but are rather some different modes of the operation <code>map</code>. There is no reason for the modes to be mutually exclusive of one another, and a use case that I mentioned above may arise.</p>
<p>I propose to add <code>filter</code> and <code>flatten</code> as optional keyword arguments to <code>Enumerable#map</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">array</span>
<span class="p">.</span><span class="nf">map</span><span class="p">(</span><span class="ss">filter: </span><span class="kp">true</span><span class="p">,</span> <span class="ss">flatten: </span><span class="mi">1</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">foo</span><span class="o">|</span>
<span class="n">bar</span> <span class="o">=</span> <span class="n">baz</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="k">next</span> <span class="k">unless</span> <span class="n">bar</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">...</span><span class="p">}</span>
<span class="k">end</span>
</code></pre>
<p>In fact, even when the two parameters are not used together, I believe it would be easier to the brain and I would feel much more comfortable to pass <code>filter: true</code> or <code>flatten: 1</code> to <code>map</code> when necessary rather than having to deicide whether to use <code>map</code> or <code>flat_map</code> or use <code>map</code> or <code>filter_map</code>.</p>
<p>Furthermore, this would make it possible to do flattening of an arbitrary depth (as specified by the parameter) during map.</p> Ruby master - Feature #17163 (Open): Rename `begin`https://bugs.ruby-lang.org/issues/171632020-09-09T03:04:22Zsawa (Tsuyoshi Sawada)
<p><code>Range#begin</code> is a getter method; it returns a value, and does not have a side effect, or does any calculation. Nevertheless, "begin" is a verb, so there is a mismatch. I would rather expect a noun.</p>
<p>It has a counterpart <code>Range#end</code>, and "end" is a noun as well as a verb, so that is not strange.</p>
<p>I propose to alias <code>Range#begin</code> to a noun or a nominal. "beginning" will work, but it may be too long, so what about "start", which works as a noun (as well as a verb)?</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Range</span><span class="c1">#start</span>
</code></pre> Ruby master - Feature #17097 (Open): `map_min`, `map_max`https://bugs.ruby-lang.org/issues/170972020-07-31T12:33:39Zsawa (Tsuyoshi Sawada)
<p><code>min</code>, <code>min_by</code>, <code>max</code>, <code>max_by</code> return the element that leads to the minimum or the maximum value, but I think it is as, or even more, frequent that we are interested in the minimum or the maximum value itself rather than the element. For example, to get the length of the longest string in an array, we do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="sx">%w[aa b cccc dd]</span><span class="p">.</span><span class="nf">max_by</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">).</span><span class="nf">length</span> <span class="c1"># => 4</span>
<span class="sx">%w[aa b cccc dd]</span><span class="p">.</span><span class="nf">map</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">).</span><span class="nf">max</span> <span class="c1"># => 4</span>
</code></pre>
<p>I propose to have methods that return the minimum or the maximum value. Temporarily calling them <code>map_min</code>, <code>map_max</code>, they should work like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="sx">%w[aa b cccc dd]</span><span class="p">.</span><span class="nf">map_max</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">)</span> <span class="c1"># => 4</span>
</code></pre>
<p><code>map_min</code>, <code>map_max</code> are implementation-centered names, so perhaps better names should replace them, just like <code>yield_self</code> was replaced by <code>then</code>.</p> Ruby master - Feature #17006 (Open): Let `Kernel#Hash` take a block to provide the default valuehttps://bugs.ruby-lang.org/issues/170062020-07-03T08:09:01Zsawa (Tsuyoshi Sawada)
<p>Sometimes, we need to create a hash that has explicit key-value pairs as well as a default value, but there has not been a way to do that at once. The most naive way is to do like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">h</span> <span class="o">=</span> <span class="p">{</span><span class="ss">a: </span><span class="mi">1</span><span class="p">,</span> <span class="ss">b: </span><span class="mi">2</span><span class="p">}</span>
<span class="n">h</span><span class="p">.</span><span class="nf">default_proc</span> <span class="o">=</span> <span class="o">-></span><span class="p">(</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="p">){</span><span class="k">raise</span> <span class="s2">"Unknown key </span><span class="si">#{</span><span class="n">k</span><span class="si">}</span><span class="s2">"</span><span class="p">}</span>
<span class="n">h</span> <span class="c1"># => ...</span>
</code></pre>
<p>A more sophisticated way is this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Hash</span><span class="p">.</span><span class="nf">new</span><span class="p">{</span><span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="k">raise</span> <span class="s2">"Unknown key </span><span class="si">#{</span><span class="n">k</span><span class="si">}</span><span class="s2">"</span><span class="p">}.</span><span class="nf">merge</span><span class="p">({</span><span class="ss">a: </span><span class="mi">1</span><span class="p">,</span> <span class="ss">b: </span><span class="mi">2</span><span class="p">})</span>
</code></pre>
<p>But that is still not short enough, and it also looks backwards, i.e., we usually want to specify the explicit key-value pairs before the default value.</p>
<p>My proposal is to allow <code>Kernel#Hash</code> to take a block that provides the default value in the same way as the block of <code>Hash.new</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Hash</span><span class="p">({</span><span class="ss">a: </span><span class="mi">1</span><span class="p">,</span> <span class="ss">b: </span><span class="mi">2</span><span class="p">}){</span><span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="k">raise</span> <span class="s2">"Unknown key </span><span class="si">#{</span><span class="n">k</span><span class="si">}</span><span class="s2">"</span><span class="p">}</span>
</code></pre> Ruby master - Bug #16842 (Closed): `inspect` prints the UTF-8 character U+0085 (NEXT LINE) verbat...https://bugs.ruby-lang.org/issues/168422020-05-09T14:35:11Zsawa (Tsuyoshi Sawada)
<p>The UTF-8 character U+0085 (NEXT LINE) is not printable, but <code>inspect</code> prints the character verbatim (within double quotation):</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mh">0x85</span><span class="p">.</span><span class="nf">chr</span><span class="p">(</span><span class="no">Encoding</span><span class="o">::</span><span class="no">UTF_8</span><span class="p">).</span><span class="nf">match?</span><span class="p">(</span><span class="sr">/\p{print}/</span><span class="p">)</span> <span class="c1"># => false</span>
<span class="mh">0x85</span><span class="p">.</span><span class="nf">chr</span><span class="p">(</span><span class="no">Encoding</span><span class="o">::</span><span class="no">UTF_8</span><span class="p">).</span><span class="nf">inspect</span>
<span class="c1">#=> "\"</span>
<span class="p">\</span><span class="s2">""</span>
</code></pre>
<p>My understanding is that non-printable characters are not printed verbatim with <code>inspect</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">.</span><span class="nf">match?</span><span class="p">(</span><span class="sr">/\p{print}/</span><span class="p">)</span> <span class="c1"># => false</span>
<span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">.</span><span class="nf">inspect</span> <span class="c1">#=> "\"\\n\""</span>
</code></pre>
<p>while printable characters are:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"a"</span><span class="p">.</span><span class="nf">match?</span><span class="p">(</span><span class="sr">/\p{print}/</span><span class="p">)</span> <span class="c1"># => true</span>
<span class="s2">"a"</span><span class="p">.</span><span class="nf">inspect</span> <span class="c1"># => "\"a\""</span>
</code></pre>
<p>I ran the following script, and found that U+0085 is the only character within the range U+0000 to U+FFFF that behaves like this.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">def</span> <span class="nf">verbatim?</span><span class="p">(</span><span class="n">char</span><span class="p">)</span>
<span class="o">!</span><span class="n">char</span><span class="p">.</span><span class="nf">inspect</span><span class="p">.</span><span class="nf">start_with?</span><span class="p">(</span><span class="sr">%r{</span><span class="se">\"\\</span><span class="sr">[a-z]}</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">printable?</span><span class="p">(</span><span class="n">char</span><span class="p">)</span>
<span class="n">char</span><span class="p">.</span><span class="nf">match?</span><span class="p">(</span><span class="sr">/\p{print}/</span><span class="p">)</span>
<span class="k">end</span>
<span class="p">(</span><span class="mh">0x0000</span><span class="o">..</span><span class="mh">0xffff</span><span class="p">).</span><span class="nf">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">i</span><span class="o">|</span>
<span class="k">begin</span>
<span class="n">char</span> <span class="o">=</span> <span class="n">i</span><span class="p">.</span><span class="nf">chr</span><span class="p">(</span><span class="no">Encoding</span><span class="o">::</span><span class="no">UTF_8</span><span class="p">)</span>
<span class="k">rescue</span> <span class="no">RangeError</span>
<span class="k">next</span>
<span class="k">end</span>
<span class="nb">puts</span> <span class="s1">'%#x'</span> <span class="o">%</span> <span class="n">i</span> <span class="k">unless</span> <span class="n">verbatim?</span><span class="p">(</span><span class="n">char</span><span class="p">)</span> <span class="o">==</span> <span class="n">printable?</span><span class="p">(</span><span class="n">char</span><span class="p">)</span>
<span class="k">end</span>
</code></pre> Ruby master - Feature #16818 (Open): Rename `Range#%` to `Range#/`https://bugs.ruby-lang.org/issues/168182020-04-26T02:15:08Zsawa (Tsuyoshi Sawada)
<p><code>Range#%</code> was introduced as an alias of <code>Range#step</code> by 14697, but it is counter-intuitive and confusing.</p>
<p>Iteration in the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">((</span><span class="mi">5</span><span class="o">..</span><span class="mi">14</span><span class="p">)</span> <span class="o">%</span> <span class="mi">3</span><span class="p">).</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="nb">p</span> <span class="n">i</span><span class="p">}</span>
<span class="c1">#>> 5</span>
<span class="c1">#>> 8</span>
<span class="c1">#>> 11</span>
<span class="c1">#>> 14</span>
</code></pre>
<p>is not based on <code>x % y</code> in any sense. In fact, actually applying <code>% 3</code> to the selected elements returns a unique value <code>2</code>, and it is not obvious how this is related to the iteration.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">11</span><span class="p">,</span> <span class="mi">14</span><span class="p">].</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="n">i</span> <span class="o">%</span> <span class="mi">3</span><span class="p">}</span>
<span class="c1"># => [2, 2, 2, 2]</span>
</code></pre>
<p>Rather, the concept seems to be based on <code>/</code>. Applying <code>/ 3</code> to the relevant elements returns a sequence <code>1, 2, 3, 4</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">11</span><span class="p">,</span> <span class="mi">14</span><span class="p">].</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="n">i</span> <span class="o">/</span> <span class="mi">3</span><span class="p">}</span>
<span class="c1"># => [1, 2, 3, 4]</span>
</code></pre>
<p>Hence, <code>(5..14).step(3)</code> can be interpreted like this: Iterate over the <a href="https://en.wikipedia.org/wiki/Equivalence_class" class="external">equivalence class</a> (quotient set) of range <code>5..14</code> yielded by <code>/ 3</code>.</p>
<p>Notice that the number of elements in <code>[5, 8, 11, 14]</code> is 4, which is <code>(14 - 5 + 1) / 3.0).ceil</code>, but is not related to <code>%</code>.</p>
<p>So I propose that the alias of <code>Range#step</code> should be <code>Range#/</code>, and <code>Range#%</code> should be deprecated as soon as possible before its use accumulates:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">((</span><span class="mi">5</span><span class="o">..</span><span class="mi">14</span><span class="p">)</span> <span class="o">/</span> <span class="mi">3</span><span class="p">).</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="nb">p</span> <span class="n">i</span><span class="p">}</span>
<span class="c1">#>> 5</span>
<span class="c1">#>> 8</span>
<span class="c1">#>> 11</span>
<span class="c1">#>> 14</span>
</code></pre>
<hr>
<p>P.S.</p>
<p>And if <code>Range#%</code> were to be introduced at all, I would rather expect it to behave like the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">((</span><span class="mi">5</span><span class="o">..</span><span class="mi">14</span><span class="p">)</span> <span class="o">%</span> <span class="mi">3</span><span class="p">).</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="nb">p</span> <span class="n">i</span><span class="p">}</span>
<span class="c1">#>> 5</span>
<span class="c1">#>> 6</span>
<span class="c1">#>> 7</span>
</code></pre>
<p>which is why I claimed above that the current <code>Range#%</code> is confusing.</p> Ruby master - Feature #16703 (Open): Namespace parameter for `Module#name`https://bugs.ruby-lang.org/issues/167032020-03-23T10:57:03Zsawa (Tsuyoshi Sawada)
<p>I often see code that intends to remove a portion of the namespace from a module/class name like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span><span class="p">;</span> <span class="k">class</span> <span class="nc">B</span> <span class="k">class</span> <span class="nc">C</span><span class="p">;</span> <span class="k">end</span> <span class="k">end</span> <span class="k">end</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">.</span><span class="nf">delete_prefix</span><span class="p">(</span><span class="s2">"A::"</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">.</span><span class="nf">delete_prefix</span><span class="p">(</span><span class="s2">"A::B::"</span><span class="p">)</span> <span class="c1"># => "C"</span>
</code></pre>
<p>I think a large portion of the use cases of the method <code>String#delete_prefix</code> belongs to such use cases.</p>
<p>I propose to let <code>Module#name</code> take an optional parameter that expresses the name space. The parameter should be either a module, string, or a symbol.</p>
<p>I am not sure whether a positional argument or a keyword argument is better.</p>
<p>Positional argument:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="s2">"A"</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">:A</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="no">A</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="s2">"A::B"</span><span class="p">)</span> <span class="c1"># => "C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">:"A::B"</span><span class="p">)</span> <span class="c1"># => "C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="p">)</span> <span class="c1"># => "C"</span>
</code></pre>
<p>Keyword argument:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: </span><span class="s2">"A"</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: :A</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: </span><span class="no">A</span><span class="p">)</span> <span class="c1"># => "B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: </span><span class="s2">"A::B"</span><span class="p">)</span> <span class="c1"># => "C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: :"A::B"</span><span class="p">)</span> <span class="c1"># => "C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="ss">namespace: </span><span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="p">)</span> <span class="c1"># => "C"</span>
</code></pre>
<p>If the module/class does not belong to the namespace given as the parameter, then perhaps it would be a good idea to prepend the name with <code>::</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span><span class="p">;</span> <span class="k">class</span> <span class="nc">B</span><span class="p">;</span> <span class="k">class</span> <span class="nc">D</span> <span class="k">end</span> <span class="k">end</span> <span class="k">end</span>
<span class="k">class</span> <span class="nc">E</span> <span class="k">end</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span> <span class="c1"># => "A::B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">D</span><span class="p">)</span> <span class="c1"># => "::A::B::C"</span>
<span class="no">A</span><span class="o">::</span><span class="no">B</span><span class="o">::</span><span class="no">C</span><span class="p">.</span><span class="nf">name</span><span class="p">(</span><span class="no">E</span><span class="p">)</span> <span class="c1"># => "::A::B::C"</span>
</code></pre> Ruby master - Bug #16685 (Closed): IRB auto indent does not work for single-line method definitionshttps://bugs.ruby-lang.org/issues/166852020-03-10T21:41:44Zsawa (Tsuyoshi Sawada)
<p>IRB auto indent does not work correctly for single line method definitions within a class. It ends up like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">001</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">class</span> <span class="nc">Foo</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">002</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">def</span> <span class="nf">a</span><span class="p">;</span> <span class="k">end</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">003</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">def</span> <span class="nf">b</span><span class="p">;</span> <span class="k">end</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">004</span><span class="p">:</span><span class="mi">0</span><span class="o">></span> <span class="k">end</span>
<span class="o">=></span> <span class="ss">:b</span>
</code></pre>
<p>I believe it should end up like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">001</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">class</span> <span class="nc">Foo</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">002</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">def</span> <span class="nf">a</span><span class="p">;</span> <span class="k">end</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">003</span><span class="p">:</span><span class="mi">1</span><span class="o">*</span> <span class="k">def</span> <span class="nf">b</span><span class="p">;</span> <span class="k">end</span>
<span class="n">irb</span><span class="p">(</span><span class="n">main</span><span class="p">):</span><span class="mo">004</span><span class="p">:</span><span class="mi">0</span><span class="o">></span> <span class="k">end</span>
<span class="o">=></span> <span class="ss">:b</span>
</code></pre> Ruby master - Feature #16684 (Open): Use the word "to" instead of "from" in backtracehttps://bugs.ruby-lang.org/issues/166842020-03-10T16:00:53Zsawa (Tsuyoshi Sawada)
<p>The most-recent-call-last order of backtrace introduced by <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: Add option to print backtrace in reverse order (stack frames first and error last) (Closed)" href="https://bugs.ruby-lang.org/issues/8661">#8661</a>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">def</span> <span class="nf">a</span><span class="p">;</span> <span class="k">raise</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">b</span><span class="p">;</span> <span class="n">a</span> <span class="k">end</span>
<span class="k">def</span> <span class="nf">c</span><span class="p">;</span> <span class="n">b</span> <span class="k">end</span>
<span class="n">c</span>
</code></pre>
<p><strong>Current</strong></p>
<pre><code>Traceback (most recent call last):
3: from foo.rb:4:in `<main>'
2: from foo.rb:3:in `c'
1: from foo.rb:2:in `b'
foo.rb:1:in `a': unhandled exception
</code></pre>
<p>is intuitive to me, and I hope it is retained. However, there are people complaining that it is confusing. I believe the unnaturalness is (at least partly) due to the fact that the word "from" is used, which made sense when backtrace was displayed in most-recent-call-first order,</p>
<pre><code>foo.rb:1:in `a': unhandled exception
1: from foo.rb:2:in `b'
2: from foo.rb:3:in `c'
3: from foo.rb:4:in `<main>'
</code></pre>
<p>but not any more. Here, my understanding is that "from" means that the previous line was called <strong>from</strong> that line.</p>
<p>I propose that, so long as the most-recent-call-last order is adopted, the word "to" should be used rather than "from", which would mean that the previous line leads <strong>to</strong> that line:</p>
<p><strong>Proposed 1</strong></p>
<pre><code>Traceback (most recent call last):
3: to foo.rb:4:in `<main>'
2: to foo.rb:3:in `c'
1: to foo.rb:2:in `b'
foo.rb:1:in `a': unhandled exception
</code></pre>
<p>Or, as an alternative, if it looks unnatural to have "to" in the first line, and to lack one before the message line, we may put it at the end of a line:</p>
<p><strong>Proposed 2</strong></p>
<pre><code>Traceback (most recent call last)
3: foo.rb:4:in `<main>' to:
2: foo.rb:3:in `c' to:
1: foo.rb:2:in `b' to:
foo.rb:1:in `a': unhandled exception
</code></pre>
<p>By using different words, it would become easier to understand the display order at a glance, and even by just looking at a single line.</p> Ruby master - Feature #16601 (Open): Let `nil.to_a` and `nil.to_h` return a fixed instancehttps://bugs.ruby-lang.org/issues/166012020-01-31T10:11:44Zsawa (Tsuyoshi Sawada)
<p>Now, <code>nil.to_s</code> returns a fixed instance:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="kp">nil</span><span class="p">.</span><span class="nf">to_s</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 440</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_s</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 440</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_s</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 440</span>
<span class="o">...</span>
</code></pre>
<p>This is useful when we have some variable <code>foo</code> which may be either <code>nil</code> or a string, and we want to check its emptiness in a condition:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">if</span> <span class="n">foo</span><span class="p">.</span><span class="nf">to_s</span><span class="p">.</span><span class="nf">empty?</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
</code></pre>
<p>By this feature, we do not (need to) create a new instance of an empty string each time we check <code>foo</code>, even when it happens to be <code>nil</code>.</p>
<p>There are similar situations with arrays and hashes. We may have variable <code>bar</code> which may be either <code>nil</code> or an array, or <code>baz</code> which may be either <code>nil</code> or a hash, and we want to check their emptiness in conditions as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">if</span> <span class="n">bar</span><span class="p">.</span><span class="nf">to_a</span><span class="p">.</span><span class="nf">empty?</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
</code></pre>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">if</span> <span class="n">baz</span><span class="p">.</span><span class="nf">to_h</span><span class="p">.</span><span class="nf">empty?</span><span class="p">;</span> <span class="o">...</span> <span class="k">end</span>
</code></pre>
<p>But unlike <code>nil.to_s</code>, the methods <code>nil.to_a</code> and <code>nil.to_h</code> create new instances of empty array or hash each time they are called:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="kp">nil</span><span class="p">.</span><span class="nf">to_a</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 540</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_a</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 560</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_a</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 580</span>
<span class="o">...</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_h</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 460</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_h</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 480</span>
<span class="kp">nil</span><span class="p">.</span><span class="nf">to_h</span><span class="p">.</span><span class="nf">object_id</span> <span class="c1"># => 500</span>
<span class="o">...</span>
</code></pre>
<p>The fact that this is somewhat inefficient discourages the use of <code>foo.to_a</code> or <code>foo.to_h</code> in such use cases.</p>
<p>I request <code>nil.to_a</code> to <code>nil.to_h</code> to return a fixed empty instance.</p> Ruby master - Bug #16599 (Closed): did_you_mean is not activated for NameError and KeyErrorhttps://bugs.ruby-lang.org/issues/165992020-01-28T20:26:23Zsawa (Tsuyoshi Sawada)
<p><a href="https://www.rubydoc.info/gems/did_you_mean/" class="external">This document</a> claims that the did_you_mean gem responds to NameError, NoMethodError, and KeyError, but it actually seems to only respond to NoMethodError.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">foo</span><span class="p">()</span>
<span class="c1"># >> NoMethodError: undefined method `foo' for main:Object</span>
<span class="c1"># >> Did you mean? for</span>
<span class="n">foo</span>
<span class="c1"># >> NameError: undefined local variable or method `foo' for main:Object</span>
<span class="no">Foo</span>
<span class="c1"># >> NameError: uninitialized constant Foo</span>
<span class="p">{</span><span class="ss">foo: </span><span class="mi">1</span><span class="p">}.</span><span class="nf">fetch</span><span class="p">(</span><span class="ss">:bar</span><span class="p">)</span>
<span class="c1"># >> KeyError: key not found: :bar</span>
</code></pre> Ruby master - Bug #16506 (Closed): Documentation for `Module#const_souce_location` is wronghttps://bugs.ruby-lang.org/issues/165062020-01-12T18:17:28Zsawa (Tsuyoshi Sawada)
<p><a href="https://ruby-doc.org/core-2.7.0/Module.html#method-i-const_source_location" class="external">https://ruby-doc.org/core-2.7.0/Module.html#method-i-const_source_location</a> says:</p>
<blockquote>
<p>Returns the Ruby source filename and line number containing <strong>first</strong> definition of constant specified.</p>
</blockquote>
<p>It should be:</p>
<blockquote>
<p>Returns the Ruby source filename and line number containing the <strong>last</strong> definition (the effective definition) of the constant specified.</p>
</blockquote>
<p>It also has an example line:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">p</span> <span class="no">Object</span><span class="p">.</span><span class="nf">const_source_location</span><span class="p">(</span><span class="s1">'A'</span><span class="p">)</span> <span class="c1"># => ["test.rb", 1] -- note it is first entry, not "continuation"</span>
</code></pre>
<p>but that may give the impression that the first-ness is due to the nature of this method. The reason <code>["test.rb", 1]</code> is returned instead of <code>["test.rb", 14]</code> is because the constant is created at line 1, and is only reopened/modified in line 14. Perhaps, this line can be changed to:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">p</span> <span class="no">Object</span><span class="p">.</span><span class="nf">const_source_location</span><span class="p">(</span><span class="s1">'A'</span><span class="p">)</span> <span class="c1"># => ["test.rb", 1] -- note 'A' is created in line 1, and is only reopened/modified in "continuation"</span>
</code></pre>
<p>Adding something like this may make it clear that it is the last definition that is returned:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">D</span> <span class="o">=</span> <span class="s1">'D1'</span>
<span class="no">D</span> <span class="o">=</span> <span class="s1">'D2'</span>
<span class="no">D</span> <span class="o">=</span> <span class="s1">'D3'</span>
<span class="o">...</span>
<span class="no">Object</span><span class="p">.</span><span class="nf">const_source_location</span><span class="p">(</span><span class="s1">'D'</span><span class="p">)</span> <span class="c1"># => returns the location that corresponds to 'D3'</span>
</code></pre> Ruby master - Misc #16481 (Third Party's Issue): Version numbering in RDoc is not consistenthttps://bugs.ruby-lang.org/issues/164812020-01-04T18:41:54Zsawa (Tsuyoshi Sawada)
<p>When you expand the "Core API" section in <a href="https://ruby-doc.org/" class="external">https://ruby-doc.org/</a>, you can see that there is version 2.6 (instead of 2.6.0). It is inconsistent with other minor versions such as 2.7.0, 2.5.0, 2.4.0, 2.3.0 and so on.</p> Ruby master - Feature #16446 (Rejected): Enumerable#take_*, Enumerable#drop_* counterparts with p...https://bugs.ruby-lang.org/issues/164462019-12-23T08:26:05Zsawa (Tsuyoshi Sawada)
<p><a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Enumerable#take_while_after (Rejected)" href="https://bugs.ruby-lang.org/issues/16441">#16441</a> led me to think about the issue more generally. When we want to split a series of iterations by the first element that satisfies (or dissatisfies) a condition, we have three factors to consider.</p>
<p>(1) Whether we want the condition to work <strong>negatively</strong> or <strong>positively</strong><br>
(2) Whether we want the first element to satisfy (or dissatisfy) the condition to be included in the <strong>left</strong> side or the <strong>right</strong> side of the split<br>
(3) Whether we want the <strong>left</strong> side or the <strong>right</strong> side in the returned output</p>
<p>This leads us to eight possible combinations to consider.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">enum</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">5</span><span class="p">].</span><span class="nf">to_enum</span>
</code></pre>
<table>
<thead>
<tr>
<th></th>
<th>(1)</th>
<th>(2)</th>
<th>(3)</th>
<th>method</th>
<th>example</th>
</tr>
</thead>
<tbody>
<tr>
<td>1</td>
<td>negatively</td>
<td>left</td>
<td>left</td>
<td><code>take_while</code></td>
<td><code>enum.foo1(&:nonzero?) # => [1, 1]</code></td>
</tr>
<tr>
<td>2</td>
<td>negatively</td>
<td>left</td>
<td>right</td>
<td><code>drop_while</code></td>
<td><code>enum.foo2(&:nonzero?) # => [0, 3, 3, 0, 5, 5]</code></td>
</tr>
<tr>
<td>3</td>
<td>negatively</td>
<td>right</td>
<td>left</td>
<td></td>
<td><code>enum.foo3(&:nonzero?) # => [1, 1, 0]</code></td>
</tr>
<tr>
<td>4</td>
<td>negatively</td>
<td>right</td>
<td>right</td>
<td></td>
<td><code>enum.foo4(&:nonzero?) # => [3, 3, 0, 5, 5]</code></td>
</tr>
<tr>
<td>5</td>
<td>positively</td>
<td>left</td>
<td>left</td>
<td></td>
<td><code>enum.foo5(&:zero?) # => [1, 1]</code></td>
</tr>
<tr>
<td>6</td>
<td>positively</td>
<td>left</td>
<td>right</td>
<td></td>
<td><code>enum.foo6(&:zero?) # => [0, 3, 3, 0, 5, 5]</code></td>
</tr>
<tr>
<td>7</td>
<td>positively</td>
<td>right</td>
<td>left</td>
<td></td>
<td><code>enum.foo7(&:zero?) # => [1, 1, 0]</code></td>
</tr>
<tr>
<td>8</td>
<td>positively</td>
<td>right</td>
<td>right</td>
<td></td>
<td><code>enum.foo8(&:zero?) # => [3, 3, 0, 5, 5]</code></td>
</tr>
</tbody>
</table>
<p>Proposal <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Enumerable#take_while_after (Rejected)" href="https://bugs.ruby-lang.org/issues/16441">#16441</a> asks for a method that corresponds to case 3 in the table above, but I think that would make the paradigm messy unless case 4 is also implemented. Either cases 3 and 4 should both be implemented, or both not. Actually, the current proposal is not about cases 3 and 4. I would leave that to <a class="issue tracker-1 status-5 priority-4 priority-default closed" title="Bug: Backport request: MJIT crashes on a certain flow of branches (Closed)" href="https://bugs.ruby-lang.org/issues/16641">#16641</a>.</p>
<p>In many use cases (including the first example in <a class="issue tracker-1 status-5 priority-4 priority-default closed" title="Bug: Backport request: MJIT crashes on a certain flow of branches (Closed)" href="https://bugs.ruby-lang.org/issues/16641">#16641</a>), we want to detect the "marker element" by which we split the iterations. In the cases above, that can be the element <code>0</code>. In such use cases, it is more natural to describe the condition in positive terms (i.e., <code>zero?</code>) rather than negative terms (i.e., <code>nonzero?</code>). (And in other use cases, it might be the other way around.) So I would like to propose methods that correspond to cases 5, 6, 7, 8 above.</p>
<p>Naming of the methods should be done systematically. As a candidate, I came up with the following:</p>
<table>
<thead>
<tr>
<th></th>
<th>method</th>
</tr>
</thead>
<tbody>
<tr>
<td>5</td>
<td><code>take_before</code></td>
</tr>
<tr>
<td>6</td>
<td><code>drop_before</code></td>
</tr>
<tr>
<td>7</td>
<td><code>take_upto</code></td>
</tr>
<tr>
<td>8</td>
<td><code>drop_upto</code></td>
</tr>
</tbody>
</table> Ruby master - Feature #16274 (Closed): Transform hash keys by a hashhttps://bugs.ruby-lang.org/issues/162742019-10-23T09:09:15Zsawa (Tsuyoshi Sawada)
<p>We have <code>Hash#transform_keys</code> and its bang version to change the keys of a hash, but that requires passing a block, which assumes that the mapping from the old keys to the new keys follows some rule. But in reality, we frequently want to change the keys where it is difficult to provide a rule. For example, suppose we have:</p>
<pre><code>hash = {created: 2019-10-23 17:54:46 +0900, updated: 2019-10-23 17:59:18 +0900, author: "foo"}
</code></pre>
<p>and want to achieve:</p>
<pre><code>{created_at: 2019-10-23 17:54:46 +0900, update_time: 2019-10-23 17:59:18 +0900, author: "foo"}
</code></pre>
<p>I request an option to change the keys of a hash not by giving a block, but by passing a hash. I came up with two options.</p>
<a name="1-Argument-for-Hashtransform_keys-and-its-bang-version"></a>
<h3 >1. Argument for <code>Hash#transform_keys</code> and its bang version<a href="#1-Argument-for-Hashtransform_keys-and-its-bang-version" class="wiki-anchor">¶</a></h3>
<p>Allow <code>Hash#transform_keys</code> to optionally take a hash argument instead of a block.</p>
<pre><code>hash.transform_keys({created: :created_at, updated: :update_time})
# => {created_at: 2019-10-23 17:54:46 +0900, update_time: 2019-10-23 17:59:18 +0900, author: "foo"}
</code></pre>
<a name="2-Argument-for-Hashslice-and-the-counterparts-in-other-classes"></a>
<h3 >2. Argument for <code>Hash#slice</code> and the counterparts in other classes<a href="#2-Argument-for-Hashslice-and-the-counterparts-in-other-classes" class="wiki-anchor">¶</a></h3>
<p>Since <code>Hash#slice</code> is often the first step of modifying a hash into some other hash form, it makes sense to let it take an optional hash argument.</p>
<pre><code>hash.slice(:created, :author, transform_keys: {created: :created_at})
# => {created_at: 2019-10-23 17:54:46 +0900, author: "foo"}
</code></pre>
<p>With option 1, it could make sense to even allow a hash argument and a block simultaneously:</p>
<pre><code>hash.transform_keys({created: :created_at, updated: :update_time}, &:to_s)
# => {"created_at" => 2019-10-23 17:54:46 +0900, "update_time" => 2019-10-23 17:59:18 +0900, "author" => "foo"}
</code></pre> Ruby master - Feature #16246 (Open): require with an optional block that is evaluated when requir...https://bugs.ruby-lang.org/issues/162462019-10-09T05:54:23Zsawa (Tsuyoshi Sawada)
<p>I have some code like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">begin</span>
<span class="nb">require</span> <span class="s2">"foo"</span>
<span class="k">rescue</span> <span class="no">LoadError</span>
<span class="nb">puts</span> <span class="s2">"You need to install foo in order to have the function A work."</span>
<span class="o">...</span>
<span class="k">end</span>
</code></pre>
<p>I request to allow <code>require</code> to take a block which is executed when requiring fails. When <code>require</code> takes a block, a <code>LoadError</code> would not be raised. The code above would then be written like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">require</span> <span class="s2">"foo"</span> <span class="k">do</span>
<span class="nb">puts</span> <span class="s2">"You need to install foo in order to have the function A work."</span>
<span class="o">...</span>
<span class="k">end</span>
</code></pre>
<p>If there is no need to particularly do anything, then it can be like</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">require</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">){}</span>
</code></pre>
<p>which will cover the use case in <a href="https://bugs.ruby-lang.org/issues/14565" class="external">https://bugs.ruby-lang.org/issues/14565</a>.</p> Ruby master - Feature #16166 (Closed): Remove exceptional treatment of *foo when it is the sole b...https://bugs.ruby-lang.org/issues/161662019-09-13T08:17:11Zsawa (Tsuyoshi Sawada)
<p>In the parameter signature of a code block for a method that is not involved in method definition or creation of lambda objects, two types of arguments <code>["a"]</code> and <code>"a"</code> are neutralized:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|</span><span class="n">foo</span><span class="p">,</span> <span class="n">bar</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => "a"</span>
<span class="n">instance_exec</span><span class="p">(</span><span class="s2">"a"</span><span class="p">){</span><span class="o">|</span><span class="n">foo</span><span class="p">,</span> <span class="n">bar</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => "a"</span>
<span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="p">,</span> <span class="o">**</span><span class="n">bar</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => ["a"]</span>
<span class="n">instance_exec</span><span class="p">(</span><span class="s2">"a"</span><span class="p">){</span><span class="o">|*</span><span class="n">foo</span><span class="p">,</span> <span class="o">**</span><span class="n">bar</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>This is the same behavior as with assignment constructions:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">foo</span><span class="p">,</span> <span class="n">bar</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">];</span> <span class="n">foo</span> <span class="c1"># => "a"</span>
<span class="n">foo</span><span class="p">,</span> <span class="n">bar</span> <span class="o">=</span> <span class="s2">"a"</span><span class="p">;</span> <span class="n">foo</span> <span class="c1"># => "a"</span>
<span class="o">*</span><span class="n">foo</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">];</span> <span class="n">foo</span> <span class="c1"># => ["a"]</span>
<span class="o">*</span><span class="n">foo</span> <span class="o">=</span> <span class="s2">"a"</span><span class="p">;</span> <span class="n">foo</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>And it contrasts with constructions involved in method definition or creation of lambda objects, where the distinction is preserved:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">lambda</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => ["a"]</span>
<span class="nb">lambda</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">(</span><span class="s2">"a"</span><span class="p">)</span> <span class="c1"># => "a"</span>
<span class="o">-></span><span class="p">(</span><span class="n">foo</span><span class="p">){</span><span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => ["a"]</span>
<span class="o">-></span><span class="p">(</span><span class="n">foo</span><span class="p">){</span><span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">(</span><span class="s2">"a"</span><span class="p">)</span> <span class="c1"># => "a"</span>
<span class="nb">lambda</span><span class="p">{</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => [["a"]]</span>
<span class="nb">lambda</span><span class="p">{</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">(</span><span class="s2">"a"</span><span class="p">)</span> <span class="c1"># => ["a"]</span>
<span class="o">-></span><span class="p">(</span><span class="o">*</span><span class="n">foo</span><span class="p">){</span><span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => [["a"]]</span>
<span class="o">-></span><span class="p">(</span><span class="o">*</span><span class="n">foo</span><span class="p">){</span><span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">(</span><span class="s2">"a"</span><span class="p">)</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>However, when <code>*foo</code> is the sole parameter of a code block for a method that is not involved in method definition or creation of lambda objects, <code>["a"]</code> and <code>"a"</code> are not neutralized:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => [["a"]]</span>
<span class="n">instance_exec</span><span class="p">(</span><span class="s2">"a"</span><span class="p">){</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>behaving in contrast to assignment constructions, and rather on a par with constructions involved in method definition or creation of lambda objects.</p>
<p>Particularly, existence or absence of another parameter <code>**bar</code> entirely changes what <code>foo</code> refers to:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => [["a"]]</span>
<span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="p">,</span> <span class="o">**</span><span class="n">bar</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>I find this behavior inconsistent and confusing. I would like to request to remove this exceptional treatment of splatted parameter <code>*foo</code> when it is the sole parameter in a code block. I request this behavior:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => ["a"]</span>
</code></pre> Ruby master - Feature #16102 (Open): `Symbol#call`https://bugs.ruby-lang.org/issues/161022019-08-14T06:59:46Zsawa (Tsuyoshi Sawada)
<p>Since symbols have a <code>to_proc</code> method, it is natural to expect that they would appear in a method chain like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="ss">:some_symbol</span><span class="p">.</span><span class="nf">to_proc</span><span class="p">.</span><span class="nf">call</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
</code></pre>
<p>In fact, I have use cases like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">arrays</span> <span class="o">=</span> <span class="p">[[</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">],</span> <span class="p">[</span><span class="s2">"c"</span><span class="p">],</span> <span class="p">[</span><span class="s2">"d"</span><span class="p">,</span> <span class="s2">"e"</span><span class="p">]]</span>
<span class="n">hashes</span> <span class="o">=</span> <span class="p">[{</span><span class="s2">"a"</span> <span class="o">=></span> <span class="mi">1</span><span class="p">},</span> <span class="p">{</span><span class="s2">"b"</span> <span class="o">=></span> <span class="mi">2</span><span class="p">,</span> <span class="s2">"c"</span> <span class="o">=></span> <span class="mi">3</span><span class="p">},</span> <span class="p">{</span><span class="s2">"d"</span> <span class="o">=></span> <span class="mi">4</span><span class="p">,</span> <span class="s2">"e"</span> <span class="o">=></span> <span class="mi">5</span><span class="p">}]</span>
<span class="ss">:product</span><span class="p">.</span><span class="nf">to_proc</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]</span>
<span class="ss">:zip</span><span class="p">.</span><span class="nf">to_proc</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => [["a", "c", "d"], ["b", nil, "e"]]</span>
<span class="ss">:union</span><span class="p">.</span><span class="nf">to_proc</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => ["a", "b", "c", "d", "e"]</span>
<span class="ss">:merge</span><span class="p">.</span><span class="nf">to_proc</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">hashes</span><span class="p">)</span> <span class="c1"># => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}</span>
</code></pre>
<p>I request <code>Symbol#call</code> to be defined, which would implicitly call <code>to_proc</code> on the receiver and then the conventional <code>Proc#call</code> on the result. Then, I can do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="ss">:product</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]</span>
<span class="ss">:zip</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => [["a", "c", "d"], ["b", nil, "e"]]</span>
<span class="ss">:union</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">arrays</span><span class="p">)</span> <span class="c1"># => ["a", "b", "c", "d", "e"]</span>
<span class="ss">:merge</span><span class="o">.</span><span class="p">(</span><span class="o">*</span><span class="n">hashes</span><span class="p">)</span> <span class="c1"># => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}</span>
</code></pre>
<p>This would solve what proposals <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Array::zip (Rejected)" href="https://bugs.ruby-lang.org/issues/6499">#6499</a>, <a class="issue tracker-2 status-7 priority-4 priority-default closed" title="Feature: Add Array#rest (with implementation) (Feedback)" href="https://bugs.ruby-lang.org/issues/6727">#6727</a>, <a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: Array#product_set (Open)" href="https://bugs.ruby-lang.org/issues/7444">#7444</a>, <a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: Array.zip and Array.product (Open)" href="https://bugs.ruby-lang.org/issues/8970">#8970</a>, <a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: Make more objects behave like "Functions" (Open)" href="https://bugs.ruby-lang.org/issues/11262">#11262</a> aim to do.</p>
<p>Notice that proposals <a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: Add Symbol#call to allow to_proc shorthand with arguments (Open)" href="https://bugs.ruby-lang.org/issues/12115">#12115</a> and <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: Symbol#call, returning method bound with arguments (Closed)" href="https://bugs.ruby-lang.org/issues/15301">#15301</a> ask for <code>Symbol#call</code>, but they ask for different things (a method that returns a proc), and are irrelevant to the current proposal.</p> Ruby master - Bug #16050 (Rejected): :@ is not parsed correctlyhttps://bugs.ruby-lang.org/issues/160502019-08-07T10:56:02Zsawa (Tsuyoshi Sawada)
<p>Symbol literal allows <code>@</code> as the first character:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="ss">:@foo</span> <span class="c1"># => :@foo</span>
</code></pre>
<p>Nevertheless, it does not allow <code>@</code> by itself:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">:</span><span class="err">@</span> <span class="c1"># >> SyntaxError: `@' without identifiers is not allowed as an instance variable name</span>
</code></pre>
<p>This resembles <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: :~@ and :!@ are not parsed correctly (Rejected)" href="https://bugs.ruby-lang.org/issues/10463">#10463</a>, but while <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: :~@ and :!@ are not parsed correctly (Rejected)" href="https://bugs.ruby-lang.org/issues/10463">#10463</a> is related to placeholder in a method name, the issue here is related to instance variable name, so I think they are different issues.</p> Ruby master - Feature #16037 (Open): Allow multiple single/double-splatted variables in `in` patt...https://bugs.ruby-lang.org/issues/160372019-08-02T11:50:30Zsawa (Tsuyoshi Sawada)
<p>Pattern matching in <code>in</code> argument seems to prohibit multiple occurrences of single/double-splatted variables.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">case</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s2">"c"</span><span class="p">,</span> <span class="s2">"d"</span><span class="p">];</span> <span class="k">in</span> <span class="o">*</span><span class="n">foo</span><span class="p">,</span> <span class="no">Integer</span><span class="p">,</span> <span class="n">bar</span><span class="p">;</span> <span class="k">end</span> <span class="c1"># >> (Not SyntaxError)</span>
<span class="k">case</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s2">"c"</span><span class="p">,</span> <span class="s2">"d"</span><span class="p">];</span> <span class="k">in</span> <span class="o">*</span><span class="n">foo</span><span class="p">,</span> <span class="no">Integer</span><span class="p">,</span> <span class="o">*</span><span class="n">bar</span><span class="p">;</span> <span class="k">end</span> <span class="c1"># >> SyntaxError: unexpected *</span>
</code></pre>
<p>However, unlike conventional constant/variable assignment, it makes sense to have multiple occurrences of single/double-splatted variables in a single pattern matching provided that we have a definite rule regarding whether the splats are greedy or not.</p>
<p>I propose the following.</p>
<ol>
<li>Relax the syntax for pattern matching in <code>in</code> argument to allow multiple occurrences of single/double-splatted variables, and set up a rule regarding whether the splats are greedy or not; preferably greedy.</li>
<li>Further, introduce new syntax for non-greedy splats <code>*?foo</code>, <code>**?foo</code>. Currently, they are syntactically invalid, so I don't think they would conflict with existing code.</li>
</ol>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">case</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s2">"c"</span><span class="p">,</span> <span class="s2">"d"</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="s2">"e"</span><span class="p">,</span> <span class="s2">"f"</span><span class="p">];</span> <span class="k">in</span> <span class="o">*</span><span class="n">foo</span><span class="p">,</span> <span class="no">Integer</span><span class="p">,</span> <span class="o">*</span><span class="n">bar</span><span class="p">;</span> <span class="n">foo</span> <span class="k">end</span> <span class="c1"># => ["a", "b", 3, "c", "d"]</span>
<span class="k">case</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s2">"c"</span><span class="p">,</span> <span class="s2">"d"</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="s2">"e"</span><span class="p">,</span> <span class="s2">"f"</span><span class="p">];</span> <span class="k">in</span> <span class="o">*</span><span class="p">?</span><span class="n">foo</span><span class="p">,</span> <span class="no">Integer</span><span class="p">,</span> <span class="o">*</span><span class="n">bar</span><span class="p">;</span> <span class="n">foo</span> <span class="k">end</span> <span class="c1"># => ["a", "b"]</span>
</code></pre> Ruby master - Bug #16010 (Rejected): Sole single-splatted variable with an array object in an ass...https://bugs.ruby-lang.org/issues/160102019-07-18T10:44:31Zsawa (Tsuyoshi Sawada)
<p>When a single splatted variable appears as the sole argument on the left side of assignment with an array on the right side, that variable is assigned the object as is on the right side:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">*</span><span class="n">foo</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">];</span> <span class="n">foo</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>This behavior looks inconsistent to me, and I am suspecting it is a bug from the reasons below.</p>
<hr>
<p>First, all other constructions that involve assignment of objects to variables work in the same way to one another, but in a different way from the above. That is, they add another nesting level of an array:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">instance_exec</span><span class="p">([</span><span class="s2">"a"</span><span class="p">]){</span><span class="o">|*</span><span class="n">foo</span><span class="o">|</span> <span class="n">foo</span><span class="p">}</span> <span class="c1"># => [["a"]]</span>
<span class="o">->*</span><span class="n">foo</span><span class="p">{</span><span class="n">foo</span><span class="p">}.</span><span class="nf">call</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => [["a"]]</span>
<span class="k">def</span> <span class="nf">baz</span><span class="p">(</span><span class="o">*</span><span class="n">foo</span><span class="p">);</span> <span class="n">foo</span> <span class="k">end</span><span class="p">;</span> <span class="n">baz</span><span class="p">([</span><span class="s2">"a"</span><span class="p">])</span> <span class="c1"># => [["a"]]</span>
</code></pre>
<p>Second, if the object on the right side of the assignment construction in question is not an array, then another level of nesting is added:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">*</span><span class="n">foo</span> <span class="o">=</span> <span class="s2">"a"</span><span class="p">;</span> <span class="n">foo</span> <span class="c1"># => ["a"]</span>
</code></pre>
<p>The splat on a variable can be understood to collect the objects into an array. However, in the first example above in which the right side object is an array, all of a sudden, the additional nesting level of array becomes absent. It is not obvious why it behaves differently when the object to be collected is already an array.</p>
<p>Third, when there is no remaining object for the splatted variable, the variable is assigned an empty array,</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">*</span><span class="n">foo</span><span class="p">,</span> <span class="n">bar</span> <span class="o">=</span> <span class="s2">"baz"</span><span class="p">;</span> <span class="n">foo</span> <span class="c1"># => []</span>
</code></pre>
<p>and when more than one objects remain for the splatted variable, the variable is assigned an array that includes those objects, even if they are arrays:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">*</span><span class="n">foo</span><span class="p">,</span> <span class="n">bar</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">],</span> <span class="p">[</span><span class="s2">"b"</span><span class="p">],</span> <span class="s2">"c"</span><span class="p">;</span> <span class="n">foo</span> <span class="c1"># => [["a"], ["b"]]</span>
</code></pre>
<p>But when there is exactly one object that corresponds to the splatted variable, that object is not included in an array, but is given as is.</p>
<hr>
<p>In short, I believe the correct behavior should be as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">*</span><span class="n">foo</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"a"</span><span class="p">];</span> <span class="n">foo</span> <span class="c1"># => [["a"]]</span>
</code></pre> Ruby master - Feature #16006 (Rejected): String count and alignment that consider multibyte chara...https://bugs.ruby-lang.org/issues/160062019-07-16T03:35:12Zsawa (Tsuyoshi Sawada)
<p>In non-proportional font, multibyte characters have twice the width of ASCII characters. Since <code>String#length</code>, <code>String#ljust</code>, <code>String#rjust</code>, and <code>String#center</code> do not take this into consideration, applying these methods do not give the desired output.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">array</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"aaあああ"</span><span class="p">,</span> <span class="s2">"bいいいいいいいい"</span><span class="p">,</span> <span class="s2">"cc"</span><span class="p">]</span>
<span class="n">col_width</span> <span class="o">=</span> <span class="n">array</span><span class="p">.</span><span class="nf">max</span><span class="p">(</span><span class="o">&</span><span class="ss">:length</span><span class="p">)</span>
<span class="n">array</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">w</span><span class="o">|</span> <span class="nb">puts</span> <span class="n">w</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="n">col_width</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)}</span>
<span class="c1"># >> aaあああ****</span>
<span class="c1"># >> bいいいいいいいい</span>
<span class="c1"># >> cc*******</span>
</code></pre>
<p>In order to do justification of strings that have multi-byte characters, we have to do something much more complicated such as the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">col_widths</span> <span class="o">=</span>
<span class="n">array</span><span class="p">.</span><span class="nf">to_h</span><span class="p">{</span><span class="o">|</span><span class="n">w</span><span class="o">|</span> <span class="p">[</span>
<span class="n">w</span><span class="p">,</span>
<span class="n">w</span>
<span class="p">.</span><span class="nf">chars</span>
<span class="p">.</span><span class="nf">partition</span><span class="p">(</span><span class="o">&</span><span class="ss">:ascii_only?</span><span class="p">)</span>
<span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="o">|</span><span class="n">ascii</span><span class="p">,</span> <span class="n">non</span><span class="o">|</span> <span class="n">ascii</span><span class="p">.</span><span class="nf">length</span> <span class="o">+</span> <span class="p">(</span><span class="n">non</span><span class="p">.</span><span class="nf">length</span> <span class="o">*</span> <span class="mi">2</span><span class="p">)}</span>
<span class="p">]}</span>
<span class="n">col_width</span> <span class="o">=</span> <span class="n">col_widths</span><span class="p">.</span><span class="nf">values</span><span class="p">.</span><span class="nf">max</span>
<span class="n">array</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">w</span><span class="o">|</span> <span class="nb">puts</span> <span class="n">w</span> <span class="o">+</span> <span class="s2">"*"</span> <span class="o">*</span> <span class="p">(</span><span class="n">col_width</span> <span class="o">-</span> <span class="n">col_widths</span><span class="p">[</span><span class="n">w</span><span class="p">])}</span>
<span class="c1"># Note that the following gives the desired alignment in non-proportional font, but may not appear so in this issue tracker.</span>
<span class="c1"># >> aaあああ*********</span>
<span class="c1"># >> bいいいいいいいい</span>
<span class="c1"># >> cc***************</span>
</code></pre>
<p>This issue seems to be common, as several webpages can be found that attempt to do something similar.</p>
<p>I propose to give the relevant methods an option to take multibyte characters into consideration. Perhaps something like the <code>proportional</code> keyword in the following may work:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"aaあああ"</span><span class="p">.</span><span class="nf">length</span><span class="p">(</span><span class="ss">proportional: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => 8</span>
<span class="s2">"aaあああ"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="mi">17</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">proportional: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "aaあああ*********"</span>
</code></pre>
<p>Then, the desired output would be given by this code:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">col_width</span> <span class="o">=</span> <span class="n">array</span><span class="p">.</span><span class="nf">max</span><span class="p">{</span><span class="o">|</span><span class="n">w</span><span class="o">|</span> <span class="n">w</span><span class="p">.</span><span class="nf">length</span><span class="p">(</span><span class="ss">proportional: </span><span class="kp">true</span><span class="p">)}</span>
<span class="n">array</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">w</span><span class="o">|</span> <span class="nb">puts</span> <span class="n">w</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="n">col_width</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">proportional: </span><span class="kp">true</span><span class="p">)}</span>
<span class="c1"># >> aaあああ*********</span>
<span class="c1"># >> bいいいいいいいい</span>
<span class="c1"># >> cc***************</span>
</code></pre> Ruby master - Bug #15987 (Closed): Let `exception` option in `Kernel#Complex`, `Kernel#Float`, `K...https://bugs.ruby-lang.org/issues/159872019-07-05T03:12:16Zsawa (Tsuyoshi Sawada)
<p>The <code>exception</code> option in <code>Kernel#Complex</code>, <code>Kernel#Float</code>, <code>Kernel#Integer</code>, and <code>Kernel#Rational</code> distinguishes <code>false</code> vs. other values.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Integer</span><span class="p">(</span><span class="s2">"z"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">false</span><span class="p">)</span> <span class="c1">#=> nil</span>
<span class="no">Integer</span><span class="p">(</span><span class="s2">"z"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#>> ArgumentError: invalid value for Integer(): "z")</span>
</code></pre>
<p>But in most other cases where a boolean notion is concerned (for example, the <code>chomp</code> option in <code>Kernel#gets</code>), the distinction is between falsy vs. truthy values.</p>
<p>I request the distinction to be falsy vs. truthy. In other words, I would like the value <code>nil</code> to work on the falsy side rather than the truthy side like this.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Integer</span><span class="p">(</span><span class="s2">"z"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">false</span><span class="p">)</span> <span class="c1">#=> nil</span>
<span class="no">Integer</span><span class="p">(</span><span class="s2">"z"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">nil</span><span class="p">)</span> <span class="c1">#=> nil</span>
</code></pre> Ruby master - Feature #15954 (Rejected): 簡単にマルチスレッドを一度に合流させるhttps://bugs.ruby-lang.org/issues/159542019-06-24T10:18:38Zsawa (Tsuyoshi Sawada)
<p>現在いるスレッド以外の全てのスレッドを現在のスレッドに合流させたいときは多いと思います。</p>
<p>その場合、一つの方法は、スレッドを生成するときにそれらを配列に蓄えておき、あとでその配列の各要素のスレッドに対して<code>join</code>をすることですが、そのためにわざわざスレッドを配列に蓄えておかなければならないのは、若干手間で無駄かなと思います。</p>
<p>それを回避する方法として、私の思いつく限りで単純な方法は次のようなものです。</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Thread</span><span class="p">.</span><span class="nf">list</span><span class="p">.</span><span class="nf">each</span><span class="p">{</span><span class="o">|</span><span class="n">t</span><span class="o">|</span> <span class="n">t</span><span class="p">.</span><span class="nf">join</span> <span class="k">unless</span> <span class="n">t</span> <span class="o">==</span> <span class="no">Thread</span><span class="p">.</span><span class="nf">current</span><span class="p">}</span>
</code></pre>
<p>しかし、ここでは現在のスレッドを合流の対象から除く条件式を入れる必要があるためにエレガントでありません。そこで、<code>Thread.list</code>から現在のスレッドを除いた配列を返すメソッドを希望します。これは<code>Dir.entries</code>だと不要なピリオドファイルが含まれる不便さから<code>Dir.children</code>が作られたのと同じ発想です。</p>
<p>あるいは、一歩進めて、<code>Thread.join_other_threads</code>のような感じで現在のスレッド以外の全てのスレッドを一気に合流させるメソッドがあってもよいと思います。</p> Ruby master - Feature #15950 (Rejected): Allow negative length in `Array#[]`, `Array#[]=`, `Array...https://bugs.ruby-lang.org/issues/159502019-06-22T03:09:43Zsawa (Tsuyoshi Sawada)
<p>To take the first n characters of a string, using <code>[]</code> is straightforward:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcdefgh"</span><span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span> <span class="c1"># => "abc"</span>
</code></pre>
<p>But to take the last n characters, we need to use n in two arguments: in the index (in negative form) in addition to the length:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcdefgh"</span><span class="p">[</span><span class="o">-</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span> <span class="c1"># => "fgh"</span>
</code></pre>
<p>This is cumbersome.</p>
<p>I wish negative length to be allowed, and be interpreted as measuring leftward (while cycling the receiver if necessary).</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcdefgh"</span><span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="o">-</span><span class="mi">3</span><span class="p">]</span> <span class="c1"># => "fgh"</span>
<span class="s2">"abcdefgh"</span><span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="o">-</span><span class="mi">3</span><span class="p">]</span> <span class="c1"># => "cde"</span>
</code></pre>
<p>If there is not enough characters or elements, it should stop at the boundary.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcdefgh"</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="o">-</span><span class="mi">3</span><span class="p">]</span> <span class="c1"># => "a"</span>
</code></pre> Ruby master - Feature #15945 (Open): Option to truncate in `String#ljust`, `String#rjust`, and `S...https://bugs.ruby-lang.org/issues/159452019-06-20T12:00:24Zsawa (Tsuyoshi Sawada)
<p>Sometimes, I need to adjust a string to an exact length: Pad if shorter, and truncate if longer. To do that, I need to combine two methods like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"12"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">5</span><span class="p">]</span> <span class="c1"># => "12***"</span>
<span class="s2">"1234567"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">5</span><span class="p">]</span> <span class="c1"># => "12345"</span>
<span class="s2">"xyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)[</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="mi">5</span><span class="p">]</span> <span class="c1"># => "**xyz"</span>
<span class="s2">"stuvwxyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)[</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="mi">5</span><span class="p">]</span> <span class="c1"># => "vwxyz"</span>
</code></pre>
<p>But that is messy, and needs a bit of thinking. It becomes even harder with centering.</p>
<p>I request an option on <code>String#ljust</code>, <code>String#rjust</code>, <code>String#center</code> to truncate the string when it is longer than the given length.</p>
<p>One way to do so may be: take a keyword <code>:truncate</code> or <code>:trunc</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"12"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "12***"</span>
<span class="s2">"1234567"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "12345"</span>
<span class="s2">"xyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "**xyz"</span>
<span class="s2">"stuvwxyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "vwxyz"</span>
<span class="s2">"abc"</span><span class="p">.</span><span class="nf">center</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "*abc*"</span>
<span class="s2">"abcdefg"</span><span class="p">.</span><span class="nf">center</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">,</span> <span class="ss">trunc: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => "bcdef"</span>
</code></pre>
<p>Another way is, when the length is negative, interpret it as truncating option.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"12"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "12***"</span>
<span class="s2">"1234567"</span><span class="p">.</span><span class="nf">ljust</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "12345"</span>
<span class="s2">"xyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "**xyz"</span>
<span class="s2">"stuvwxyz"</span><span class="p">.</span><span class="nf">rjust</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "vwxyz"</span>
<span class="s2">"abc"</span><span class="p">.</span><span class="nf">center</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "*abc*"</span>
<span class="s2">"abcdefg"</span><span class="p">.</span><span class="nf">center</span><span class="p">(</span><span class="o">-</span><span class="mi">5</span><span class="p">,</span> <span class="s2">"*"</span><span class="p">)</span> <span class="c1"># => "bcdef"</span>
</code></pre>
<p>But the second way changes the current behavior.</p> Ruby master - Feature #15919 (Rejected): Offset parameter for `Integer#times`https://bugs.ruby-lang.org/issues/159192019-06-13T09:18:47Zsawa (Tsuyoshi Sawada)
<p>I request an optional argument on <code>Integer#times</code> to set the offset at start, just like <code>Enumerator#with_index</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mi">5</span><span class="p">.</span><span class="nf">times</span><span class="p">(</span><span class="mi">3</span><span class="p">){</span><span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="nb">p</span> <span class="n">i</span><span class="p">}</span>
<span class="c1"># >> 3</span>
<span class="c1"># >> 4</span>
<span class="c1"># >> 5</span>
<span class="c1"># >> 6</span>
<span class="c1"># >> 7</span>
</code></pre>
<p>I think there are plenty of use cases, especially when the offset is 1.</p> Ruby master - Feature #15722 (Feedback): `Kernel#case?`https://bugs.ruby-lang.org/issues/157222019-03-22T07:12:32Zsawa (Tsuyoshi Sawada)
<p>I often want to use <code>===</code> to match a single object on the right side against multiple objects on the left, as is used in <code>case</code>-constructions, just to return a truth value, and end up writing like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">bar</span> <span class="c1"># => "bar"</span>
<span class="n">flag1</span> <span class="o">=</span> <span class="k">case</span> <span class="n">bar</span><span class="p">;</span> <span class="k">when</span> <span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">,</span> <span class="s2">"baz"</span><span class="p">;</span> <span class="kp">true</span><span class="p">;</span> <span class="k">end</span> <span class="c1"># => true</span>
<span class="n">flag2</span> <span class="o">=</span> <span class="k">case</span> <span class="n">bar</span><span class="p">;</span> <span class="k">when</span> <span class="no">Symbol</span><span class="p">,</span> <span class="no">String</span><span class="p">;</span> <span class="kp">true</span><span class="p">;</span> <span class="k">end</span> <span class="c1"># => true</span>
</code></pre>
<p>I propose <code>Kernel#case?</code> that should work like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">bar</span> <span class="c1"># => "bar"</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">case?</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">,</span> <span class="s2">"baz"</span><span class="p">)</span> <span class="c1"># => true</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">case?</span><span class="p">(</span><span class="s2">"qux"</span><span class="p">)</span> <span class="c1"># => false</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">case?</span><span class="p">(</span><span class="no">Symbol</span><span class="p">,</span> <span class="no">String</span><span class="p">)</span> <span class="c1"># => true</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">case?</span><span class="p">(</span><span class="no">Array</span><span class="p">)</span> <span class="c1"># => false</span>
<span class="n">bar</span><span class="p">.</span><span class="nf">case?</span> <span class="c1"># => false</span>
</code></pre>
<p>It is similar to Rails' <code>in?</code>, but it differs from it in that it uses <code>===</code> for comparison, not <code>==</code>.</p>
<p>Or, alternatively, allowing <code>Kernel#instance_of?</code> and <code>Kernel#kind_of?</code> to allow multiple arguments may be a compromise.</p> Ruby master - Bug #15708 (Rejected): Implicit numbered argument decomposes an arrayhttps://bugs.ruby-lang.org/issues/157082019-03-19T11:08:39Zsawa (Tsuyoshi Sawada)
<p>In the following, <code>@1</code> refers to the entire item iterated:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">x</span><span class="o">|</span> <span class="n">x</span><span class="p">}</span> <span class="c1"># => [1, 2, 3]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="err">@</span><span class="mi">1</span><span class="p">}</span> <span class="c1"># => [1, 2, 3]</span>
</code></pre>
<p>whereas in the following, <code>@1</code> refers to the first item achieved by decomposing the item iterated, behaving the same as <code>x</code> given by <code>|(x)|</code> rather than by <code>|x|</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[[</span><span class="mi">1</span><span class="p">],</span> <span class="p">[</span><span class="mi">2</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">]]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">x</span><span class="o">|</span> <span class="n">x</span><span class="p">}</span> <span class="c1"># => [[1], [2], [3]]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="p">(</span><span class="n">x</span><span class="p">)</span><span class="o">|</span> <span class="n">x</span><span class="p">}</span> <span class="c1"># => [1, 2, 3]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="err">@</span><span class="mi">1</span><span class="p">}</span> <span class="c1"># => [1, 2, 3]</span>
</code></pre>
<p>Is this intended?</p> Ruby master - Misc #15654 (Open): Documentation for Complex is wrong or misleadinghttps://bugs.ruby-lang.org/issues/156542019-03-11T08:43:36Zsawa (Tsuyoshi Sawada)
<p>The documentation for <code>Complex</code> <a href="https://ruby-doc.org/core-2.6/Complex.html" class="external">https://ruby-doc.org/core-2.6/Complex.html</a> says or implies that a complex can be created by literal like <code>2+1i</code>, but that is actually calling the method <code>+</code> on receiver <code>2</code> with argument <code>1i</code>. The description should be changed to make it clear that <code>2+ 1i</code> is not a literal but is applying a method.</p> Ruby master - Feature #15627 (Open): Appearance of custom singleton classeshttps://bugs.ruby-lang.org/issues/156272019-02-28T11:47:27Zsawa (Tsuyoshi Sawada)
<p>When I have a singleton class <code>AClass</code> of an instance <code>a</code> of a custom class <code>A</code>,</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span><span class="p">;</span> <span class="k">end</span>
<span class="n">a</span> <span class="o">=</span> <span class="no">A</span><span class="p">.</span><span class="nf">new</span>
<span class="no">AClass</span> <span class="o">=</span> <span class="n">a</span><span class="p">.</span><span class="nf">singleton_class</span>
</code></pre>
<p>i) even though the singleton class of <code>nil</code>, <code>false</code>, and <code>true</code> are referred to by their assigned constant names, the singleton class <code>AClass</code> of <code>a</code> is not:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="kp">nil</span><span class="p">.</span><span class="nf">singleton_class</span> <span class="c1">#=> NilClass</span>
<span class="kp">false</span><span class="p">.</span><span class="nf">singleton_class</span> <span class="c1">#=> FalseClass</span>
<span class="kp">true</span><span class="p">.</span><span class="nf">singleton_class</span> <span class="c1">#=> TrueClass</span>
<span class="n">a</span><span class="p">.</span><span class="nf">singleton_class</span> <span class="c1">#=> #<Class:#<A:0x00007fda832a7eb0>></span>
</code></pre>
<p>ii) even though the singleton class of <code>nil</code>, <code>false</code>, and <code>true</code> appear as their class, the singleton class <code>AClass</code> of <code>a</code> does not:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="kp">nil</span><span class="p">.</span><span class="nf">class</span> <span class="c1">#=> NilClass</span>
<span class="kp">false</span><span class="p">.</span><span class="nf">class</span> <span class="c1">#=> FalseClass</span>
<span class="kp">true</span><span class="p">.</span><span class="nf">class</span> <span class="c1">#=> TrueClass</span>
<span class="n">a</span><span class="p">.</span><span class="nf">class</span> <span class="c1">#=> A</span>
</code></pre>
<p>This contrast between <code>nil</code>, <code>false</code>, and <code>true</code> on the one hand and <code>a</code> on the other is confusing. I am actually not sure if this is intended behaviour It may be related to</p>
<ul>
<li><a href="https://bugs.ruby-lang.org/issues/15608" class="external">https://bugs.ruby-lang.org/issues/15608</a></li>
<li><a href="https://bugs.ruby-lang.org/issues/14895" class="external">https://bugs.ruby-lang.org/issues/14895</a></li>
</ul>
<p>I expect <code>AClass</code> to behave the same as with <code>NilClass</code>, <code>FalseClass</code>, and <code>TrueClass</code>. I expect:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">singleton_class</span> <span class="c1">#=> AClass</span>
<span class="n">a</span><span class="p">.</span><span class="nf">class</span> <span class="c1">#=> AClass</span>
</code></pre>
<p>If the current behaviour is intended, I would like this to become a feature request.</p> Ruby master - Feature #15612 (Feedback): A construct to restrict the scope of local variableshttps://bugs.ruby-lang.org/issues/156122019-02-19T12:42:21Zsawa (Tsuyoshi Sawada)
<p>We sometimes have local variables that are to be used only to keep track of some temporal states/values during a short routine:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="o">...</span>
<span class="n">foo</span> <span class="o">=</span> <span class="n">some_initial_value</span>
<span class="n">some_routine_that_uses_foo</span>
<span class="o">...</span>
</code></pre>
<p>Currently, the scope of local variables are either a proc, a block, <code>loop</code> body, a method definition, or a class/module definition, but such routines are sometimes just only a part of them.</p>
<p>In order to improve readability of the code by explicitly indicating the scope of such local variables, and to avoid pollution by the variable, I propose to have some construct to restrict the scope of local variables.</p>
<p>One possibility, without adding a new keyword to the current syntax, is to use the <code>begin</code>...<code>end</code> construct. The expected behavior would be:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">begin</span>
<span class="n">foo</span> <span class="o">=</span> <span class="s2">"foo"</span>
<span class="n">foo</span> <span class="c1"># => "foo"</span>
<span class="k">end</span>
<span class="n">foo</span> <span class="c1"># => `nil`, or "Undefined local variable or method error"</span>
</code></pre>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">foo</span> <span class="o">=</span> <span class="s2">"bar"</span>
<span class="k">begin</span>
<span class="n">foo</span> <span class="o">=</span> <span class="s2">"foo"</span>
<span class="n">foo</span> <span class="c1"># => "foo"</span>
<span class="k">end</span>
<span class="n">foo</span> <span class="c1"># => "bar"</span>
</code></pre>
<p>Or, does this break the existing code too much? If so, can a new construct be added to the current syntax?</p> Ruby master - Feature #15589 (Closed): `Numeric#zero?` is much slower than `== 0`https://bugs.ruby-lang.org/issues/155892019-02-06T09:34:41Zsawa (Tsuyoshi Sawada)
<p>My understanding is that the predicate method <code>Numeric#zero?</code> is not only a shorthand for <code>== 0</code>, but is also optimized for frequent patterns. If <code>zero?</code> is not faster than <code>== 0</code>, then it loses its reason for existence.</p>
<p>However, According to benchmarks on my environment, <code>number.zero?</code> is around 1.23 times to 1.64 times slower than <code>number == 0</code> when <code>number</code> is an <code>Integer</code>, <code>Rational</code>, or <code>Complex</code>. It is faster only when <code>number</code> is a <code>Float</code>.</p>
<p>And with <code>number.nonzero?</code>, it is even worse. It is about 1.88 times to 4.35 times slower than <code>number != 0</code>.</p>
<p>I think there is something wrong with this, and it should be possible to optimize these methods, which has somehow been missed.</p> Ruby master - Feature #15562 (Open): `String#split` option to suppress the initial empty substringhttps://bugs.ruby-lang.org/issues/155622019-01-25T07:19:12Zsawa (Tsuyoshi Sawada)
<p><code>String#split</code> returns an empty substring if any at the beginning of the original string, even though it does not return an empty substring at the end of the original string:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">)</span> <span class="c1"># => ["", "b"]</span>
</code></pre>
<p>This is probably heritage from Perl or AWK, and may have some use cases, but in some (if not most) use cases, this looks asymmetric, and the initial empty string is unnatural and often requires some additional code to remove it. I propose to give an option to <code>String#split</code> to suppress it, perhaps like this (with <code>true</code> being the default):</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">initial_empty_string: </span><span class="kp">false</span><span class="p">)</span> <span class="c1"># => ["b"]</span>
<span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">initial_empty_string: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => ["", "b"]</span>
<span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"ba"</span><span class="p">,</span> <span class="ss">initial_empty_string: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => ["b"]</span>
</code></pre>
<p>This does not mean to suppress empty strings in the middle. So it should work like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"aaaba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">initial_empty_string: </span><span class="kp">false</span><span class="p">)</span> <span class="c1"># => ["", "", "b"]</span>
<span class="s2">"aaaba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">initial_empty_string: </span><span class="kp">true</span><span class="p">)</span> <span class="c1"># => ["", "", "", "b"]</span>
</code></pre>
<p>Or may be we can even go on further to control both the initial and the final ones like (with <code>:initial</code> being the default):</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">terminal_empty_string: :none</span><span class="p">)</span> <span class="c1"># => ["b"]</span>
<span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">terminal_empty_string: :initial</span><span class="p">)</span> <span class="c1"># => ["", "b"]</span>
<span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">terminal_empty_string: :final</span><span class="p">)</span> <span class="c1"># => ["b", ""]</span>
<span class="s2">"aba"</span><span class="p">.</span><span class="nf">split</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="ss">terminal_empty_string: :both</span><span class="p">)</span> <span class="c1"># => ["", "b", ""]</span>
</code></pre> Ruby master - Feature #15557 (Open): A new class that stores a condition and the previous receiverhttps://bugs.ruby-lang.org/issues/155572019-01-23T09:15:54Zsawa (Tsuyoshi Sawada)
<p>I often see code like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">foo</span> <span class="o">=</span> <span class="n">default_definition</span>
<span class="n">foo</span> <span class="o">=</span> <span class="n">some_method</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span> <span class="k">if</span> <span class="n">some_condition</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="n">foo</span> <span class="o">=</span> <span class="n">another_method</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span> <span class="k">if</span> <span class="n">another_condition</span><span class="p">(</span><span class="n">foo</span><span class="p">)</span>
<span class="o">...</span>
</code></pre>
<p>It would be nice if we can write this as a method chain. Since we now have the method <code>then</code>, I thought it would be a nice fit to introduce a method called <code>when</code>, such that putting it right in front of <code>then</code> would execute the <code>then</code> method as ordinarily only when the condition is satisfied, and returns the previous receiver otherwise so that the code above can be rewritten as:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">foo</span> <span class="o">=</span>
<span class="n">default_definition</span>
<span class="p">.</span><span class="nf">when</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">some_condition</span><span class="p">(</span><span class="n">foo</span><span class="p">)}</span>
<span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">some_method</span><span class="p">(</span><span class="n">foo</span><span class="p">)}</span>
<span class="p">.</span><span class="nf">when</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">another_condition</span><span class="p">(</span><span class="n">foo</span><span class="p">)}</span>
<span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="o">|</span><span class="n">foo</span><span class="o">|</span> <span class="n">another_method</span><span class="p">(</span><span class="n">foo</span><span class="p">)}</span>
</code></pre>
<p>This proposal is also a generalization of what I intended to cover by <a href="https://bugs.ruby-lang.org/issues/13807" class="external">https://bugs.ruby-lang.org/issues/13807</a>. That is,</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">some_condition</span> <span class="p">?</span> <span class="n">a</span> <span class="p">:</span> <span class="n">b</span>
</code></pre>
<p>would rewritten as:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">when</span><span class="p">(</span><span class="o">&</span><span class="ss">:some_condition</span><span class="p">).</span><span class="nf">then</span><span class="p">{</span><span class="n">b</span><span class="p">}</span>
</code></pre>
<p>The proposal can be implemented by introducing a class called <code>Condition</code>, which stores a condition and the previous receiver, and works with <code>then</code> in a particular way.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Object</span>
<span class="k">def</span> <span class="nf">when</span>
<span class="no">Condition</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="nb">self</span><span class="p">,</span> <span class="k">yield</span><span class="p">(</span><span class="nb">self</span><span class="p">))</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">class</span> <span class="nc">Condition</span>
<span class="k">def</span> <span class="nf">initialize</span> <span class="n">default</span><span class="p">,</span> <span class="n">condition</span>
<span class="vi">@default</span><span class="p">,</span> <span class="vi">@condition</span> <span class="o">=</span> <span class="n">default</span><span class="p">,</span> <span class="n">condition</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">then</span>
<span class="vi">@condition</span> <span class="p">?</span> <span class="k">yield</span><span class="p">(</span><span class="vi">@default</span><span class="p">)</span> <span class="p">:</span> <span class="vi">@default</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>And additionally, if we introduce a negated method <code>unless</code> (or <code>else</code>) as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Object</span>
<span class="k">def</span> <span class="nf">unless</span>
<span class="no">Condition</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="nb">self</span><span class="p">,</span> <span class="o">!</span><span class="k">yield</span><span class="p">(</span><span class="nb">self</span><span class="p">))</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>then we can use that for purposes such as validation of a variable as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">bar</span> <span class="o">=</span>
<span class="nb">gets</span>
<span class="p">.</span><span class="nf">unless</span><span class="p">{</span><span class="o">|</span><span class="n">bar</span><span class="o">|</span> <span class="n">some_validation</span><span class="p">(</span><span class="n">bar</span><span class="p">)}</span>
<span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="k">raise</span> <span class="s2">"The input is bad."</span><span class="p">}</span>
<span class="p">.</span><span class="nf">unless</span><span class="p">{</span><span class="o">|</span><span class="n">bar</span><span class="o">|</span> <span class="n">another_validation</span><span class="p">(</span><span class="n">bar</span><span class="p">)}</span>
<span class="p">.</span><span class="nf">then</span><span class="p">{</span><span class="k">raise</span> <span class="s2">"The input is bad in another way."</span><span class="p">}</span>
</code></pre> Ruby master - Feature #15523 (Open): Let `Range#begin` and `Range#end` be aliases of Range#first ...https://bugs.ruby-lang.org/issues/155232019-01-11T04:44:48Zsawa (Tsuyoshi Sawada)
<p>My understanding is that <code>Range#begin</code> and <code>Range#end</code>'s features are just subsets of <code>Range#first</code> and <code>Range#last</code>, respectively. And since they are slightly confusing with the keywords <code>begin</code> and <code>end</code>, I propose to either:</p>
<ul>
<li>Let <code>Range#begin</code> and <code>Range#end</code> be aliases of <code>Range#first</code> and <code>Range#last</code>, respectively, or</li>
<li>Let <code>Range#begin</code> and <code>Range#end</code> be obsolete after a migration path of waning against their use and recommending the use of <code>Range#first</code> and <code>Range#last</code> instead.</li>
</ul> Ruby master - Feature #15381 (Open): Let double splat call `to_h` implicitlyhttps://bugs.ruby-lang.org/issues/153812018-12-05T08:25:04Zsawa (Tsuyoshi Sawada)
<p>The single splat calls <code>to_a</code> implicitly on the object (if it is not an array already) so that, for example, we have the convenience of writing conditions in an array literal:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span>
<span class="o">*</span><span class="p">(</span><span class="ss">:foo</span> <span class="k">if</span> <span class="n">some_condition</span><span class="p">),</span>
<span class="o">*</span><span class="p">(</span><span class="ss">:bar</span> <span class="k">if</span> <span class="n">another_condition</span><span class="p">),</span>
<span class="p">]</span>
</code></pre>
<p>And the ampersand implicitly calls <code>to_proc</code> on the object (if it is not a proc already) so that we can substitute a block with an ampersand followed by a symbol:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">some_method</span><span class="p">(</span><span class="o">&</span><span class="ss">:some_method_name</span><span class="p">)</span>
</code></pre>
<p>Unlike the single splat and ampersand, the double splat does not seem to implicitly call a corresponding method. I propose that the double splat should call <code>to_h</code> implicitly on the object if it not already a Hash so that we can, for example, write a condition in a hash literal as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">h</span> <span class="o">=</span> <span class="p">{</span>
<span class="o">**</span><span class="p">({</span><span class="ss">a: </span><span class="mi">1</span><span class="p">}</span> <span class="k">if</span> <span class="n">some_condition</span><span class="p">),</span>
<span class="o">**</span><span class="p">({</span><span class="ss">b: </span><span class="mi">2</span><span class="p">)</span> <span class="k">if</span> <span class="n">another_condition</span><span class="p">),</span>
<span class="p">}</span>
</code></pre>
<p>There may be some other benefits of this feature that I have not noticed yet.</p> Ruby master - Feature #14443 (Closed): Omit 'pattern' parameter in '(g)sub(!)' when 'hash' is givenhttps://bugs.ruby-lang.org/issues/144432018-02-05T05:58:45Zsawa (Tsuyoshi Sawada)
<p>When <code>(g)sub(!)</code> takes a hash as the second argument, in almost all use cases, the first argument expresses the union of keys of the hash. In the following, <code>/[abc]/</code> is the union of the keys <code>"a"</code>, <code>"b"</code>, <code>"c"</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"blahblah"</span><span class="p">.</span><span class="nf">sub</span><span class="p">(</span><span class="sr">/[abc]/</span><span class="p">,</span> <span class="p">{</span><span class="s2">"a"</span> <span class="o">=></span> <span class="s2">"A"</span><span class="p">,</span> <span class="s2">"b"</span> <span class="o">=></span> <span class="s2">"B"</span><span class="p">,</span> <span class="s2">"c"</span> <span class="o">=></span> <span class="s2">"C"</span><span class="p">})</span>
</code></pre>
<p>I feel this redundant and not efficient. Hence I propose to let the current first argument be optional when a hash is given. The following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"blahblah"</span><span class="p">.</span><span class="nf">sub</span><span class="p">(</span><span class="s2">"a"</span> <span class="o">=></span> <span class="s2">"A"</span><span class="p">,</span> <span class="s2">"b"</span> <span class="o">=></span> <span class="s2">"B"</span><span class="p">,</span> <span class="s2">"c"</span> <span class="o">=></span> <span class="s2">"C"</span><span class="p">)</span>
</code></pre>
<p>should be equivalent to:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"blahblah"</span><span class="p">.</span><span class="nf">sub</span><span class="p">(</span><span class="n">pattern</span><span class="p">,</span> <span class="p">{</span><span class="s2">"a"</span> <span class="o">=></span> <span class="s2">"A"</span><span class="p">,</span> <span class="s2">"b"</span> <span class="o">=></span> <span class="s2">"B"</span><span class="p">,</span> <span class="s2">"c"</span> <span class="o">=></span> <span class="s2">"C"</span><span class="p">})</span>
</code></pre>
<p>where:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">pattern</span> <span class="o">=</span> <span class="no">Regexp</span><span class="p">.</span><span class="nf">union</span><span class="p">(</span><span class="o">*</span><span class="p">{</span><span class="s2">"a"</span> <span class="o">=></span> <span class="s2">"A"</span><span class="p">,</span> <span class="s2">"b"</span> <span class="o">=></span> <span class="s2">"B"</span><span class="p">,</span> <span class="s2">"c"</span> <span class="o">=></span> <span class="s2">"C"</span><span class="p">}.</span><span class="nf">keys</span><span class="p">.</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">k</span><span class="o">|</span> <span class="no">Regexp</span><span class="p">.</span><span class="nf">escape</span><span class="p">(</span><span class="n">k</span><span class="p">)})</span>
</code></pre> Ruby master - Feature #14022 (Rejected): String#surroundhttps://bugs.ruby-lang.org/issues/140222017-10-18T04:38:07Zsawa (Tsuyoshi Sawada)
<p>After joining the elements of an array into a string using <code>Array#join</code>, I frequently need to put substrings before and after the string. In such case, I would have to use either of the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">].</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">).</span><span class="nf">prepend</span><span class="p">(</span><span class="s2">"<"</span><span class="p">).</span><span class="nf">concat</span><span class="p">(</span><span class="s2">">"</span><span class="p">)</span> <span class="c1"># => "<1, 2, 3>"</span>
<span class="s2">"<</span><span class="si">#{</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">].</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">)</span><span class="si">}</span><span class="s2">>"</span> <span class="c1"># => "<1, 2, 3>"</span>
<span class="s2">"<"</span> <span class="o">+</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">].</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">)</span> <span class="o">+</span> <span class="s2">">"</span> <span class="c1"># => "<1, 2, 3>"</span>
</code></pre>
<p>but none of them is concise enough. I wish there were <code>String#surround</code> that works like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">].</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">).</span><span class="nf">surround</span><span class="p">(</span><span class="s2">"<"</span><span class="p">,</span> <span class="s2">">"</span><span class="p">)</span> <span class="c1"># => "<1, 2, 3>"</span>
</code></pre> Ruby master - Feature #13807 (Closed): A method to filter the receiver against some conditionhttps://bugs.ruby-lang.org/issues/138072017-08-11T20:38:09Zsawa (Tsuyoshi Sawada)
<p>I frequently see code that uses some value if that value satisfies a certain condition, and something else otherwise.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">some_condition</span> <span class="p">?</span> <span class="n">a</span> <span class="p">:</span> <span class="n">b</span>
</code></pre>
<p>And in most cases, the value of <code>a</code> is non-nil when the condition is satisfied.</p>
<p>I propose to have a method, perhaps named <code>verify</code>, which would implemented to be equivalent to this definition:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Object</span>
<span class="k">def</span> <span class="nf">verify</span>
<span class="nb">self</span> <span class="k">if</span> <span class="k">yield</span><span class="p">(</span><span class="nb">self</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>Then, we can write the expression above (assuming <code>a</code> is non-nil when the condition is satisfied) like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">verify</span><span class="p">{</span><span class="o">|</span><span class="n">a</span><span class="o">|</span> <span class="n">a</span><span class="p">.</span><span class="nf">some_condition</span><span class="p">}</span> <span class="o">||</span> <span class="n">b</span>
</code></pre>
<p>Perhaps it would also be useful to do something like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">verify</span><span class="p">{</span><span class="o">|</span><span class="n">a</span><span class="o">|</span> <span class="n">a</span><span class="p">.</span><span class="nf">some_condition</span><span class="p">}</span><span class="o">&</span><span class="p">.</span><span class="nf">chaining_of_more_methods</span>
</code></pre> Ruby master - Feature #13123 (Closed): NilClass#dighttps://bugs.ruby-lang.org/issues/131232017-01-11T07:07:02Zsawa (Tsuyoshi Sawada)
<p>We now have <code>Hash#dig</code>. We often have a variable that is either a hash or nil but we are not sure which. In such cases, it would be convenient if we can apply <code>dig</code> without conditioning on whether it is a hash or nil.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">h</span> <span class="o">=</span> <span class="p">{</span><span class="ss">a: </span><span class="mi">1</span><span class="p">}</span>
<span class="n">h</span><span class="p">.</span><span class="nf">dig</span><span class="p">(</span><span class="ss">:a</span><span class="p">)</span> <span class="c1"># => 1</span>
<span class="n">h</span> <span class="o">=</span> <span class="kp">nil</span>
<span class="n">h</span><span class="p">.</span><span class="nf">dig</span><span class="p">(</span><span class="ss">:a</span><span class="p">)</span> <span class="c1"># => nil</span>
</code></pre> Ruby master - Feature #12775 (Rejected): Random subset of arrayhttps://bugs.ruby-lang.org/issues/127752016-09-20T04:50:00Zsawa (Tsuyoshi Sawada)
<p>I often see use cases to randomly sample a subset from an array like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">1</span><span class="p">]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">sample</span><span class="p">(</span><span class="nb">rand</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="nf">length</span> <span class="o">+</span> <span class="mi">1</span><span class="p">))</span> <span class="c1"># => [2, 6, 6, 3]</span>
</code></pre>
<p>I request extending <code>Array#sample</code> to let it take an option (such as <code>:arbitrary</code>) for doing that:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">sample</span><span class="p">(</span><span class="ss">:arbitrary</span><span class="p">)</span> <span class="c1"># => [2, 6, 6, 3]</span>
</code></pre>
<p>or perhaps having an independent method (like <code>samples</code>) to do it.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span><span class="p">.</span><span class="nf">samples</span> <span class="c1"># => [2, 6, 6, 3]</span>
</code></pre> Ruby master - Feature #12698 (Feedback): Method to delete a substring by regex matchhttps://bugs.ruby-lang.org/issues/126982016-08-24T04:37:35Zsawa (Tsuyoshi Sawada)
<p>There is frequent need to delete a substring from a string. There already are methods <code>String#delete</code> and <code>String#delete!</code>, but their feature is a little bit different from the use cases that I am mentioning here.</p>
<p>I request methods that take a string or a regexp as an argument, and delete the matches from the receiver string. I am not sure of the method name, and I will use the term <code>remove</code> here. It can be named in some other better way. I request all combinations of global vs. local, and non-destructive vs. destructive. The expected feature is something like the following. First, the non-destructive ones:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcabc"</span><span class="p">.</span><span class="nf">remove</span><span class="p">(</span><span class="s2">"c"</span><span class="p">)</span> <span class="c1"># => "ababc"</span>
<span class="s2">"abcabc"</span><span class="p">.</span><span class="nf">remove</span><span class="p">(</span><span class="sr">/\zc/</span><span class="p">)</span> <span class="c1"># => "abcab"</span>
<span class="s2">"abcabc"</span><span class="p">.</span><span class="nf">gremove</span><span class="p">(</span><span class="s2">"c"</span><span class="p">)</span> <span class="c1"># => "abab"</span>
<span class="s2">"abcabc"</span><span class="p">.</span><span class="nf">gremove</span><span class="p">(</span><span class="sr">/c/</span><span class="p">)</span> <span class="c1"># => "abab"</span>
</code></pre>
<p>Then, the destructive ones:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">s</span> <span class="o">=</span> <span class="s2">"abcabc"</span>
<span class="n">s</span><span class="p">.</span><span class="nf">remove!</span><span class="p">(</span><span class="s2">"c"</span><span class="p">)</span> <span class="c1"># => "ababc"</span>
<span class="n">s</span> <span class="c1"># => "ababc"</span>
<span class="n">s</span> <span class="o">=</span> <span class="s2">"abcabc"</span>
<span class="n">s</span><span class="p">.</span><span class="nf">gremove!</span><span class="p">(</span><span class="s2">"d"</span><span class="p">)</span> <span class="c1"># => nil</span>
<span class="n">s</span> <span class="c1"># => "abcabc"</span>
</code></pre>
<p>Using this, cases like <a href="https://bugs.ruby-lang.org/issues/12694" class="external">https://bugs.ruby-lang.org/issues/12694</a> would be just special cases. They can be handled like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"abcdef"</span><span class="p">.</span><span class="nf">remove</span><span class="p">(</span><span class="sr">/\Aabc/</span><span class="p">)</span> <span class="c1"># => "def"</span>
</code></pre> Ruby master - Feature #12648 (Open): `Enumerable#sort_by` with descending optionhttps://bugs.ruby-lang.org/issues/126482016-08-02T09:57:26Zsawa (Tsuyoshi Sawada)
<p>I would like to pass an optional argument to <code>Enumerable#sort_by</code> or <code>Enumerable#sort_by!</code> to allow descending sort. When the sort key is singular, this could be done by passing a single optinal boolean variable that represents ascending when <code>false</code> (default) and descending when <code>true</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="o">&</span><span class="ss">:itself</span><span class="p">)</span> <span class="c1"># => [1, 2, 3]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">false</span><span class="p">,</span> <span class="o">&</span><span class="ss">:itself</span><span class="p">)</span> <span class="c1"># => [1, 2, 3]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">true</span><span class="p">,</span> <span class="o">&</span><span class="ss">:itself</span><span class="p">)</span> <span class="c1"># => [3, 2, 1]</span>
</code></pre>
<p>When there are multiple sort keys, corresponding numbers of arguments should be passed:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="p">[</span><span class="n">e</span> <span class="o">%</span> <span class="mi">2</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [0, 2, 1, 3]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">false</span><span class="p">,</span> <span class="kp">false</span><span class="p">){</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="p">[</span><span class="n">e</span> <span class="o">%</span> <span class="mi">2</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [0, 2, 1, 3]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">false</span><span class="p">,</span> <span class="kp">true</span><span class="p">){</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="p">[</span><span class="n">e</span> <span class="o">%</span> <span class="mi">2</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [2, 0, 3, 1]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">true</span><span class="p">,</span> <span class="kp">false</span><span class="p">){</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="p">[</span><span class="n">e</span> <span class="o">%</span> <span class="mi">2</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [1, 3, 0, 2]</span>
<span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">].</span><span class="nf">sort_by</span><span class="p">(</span><span class="kp">true</span><span class="p">,</span> <span class="kp">true</span><span class="p">){</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="p">[</span><span class="n">e</span> <span class="o">%</span> <span class="mi">2</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [3, 1, 2, 0]</span>
</code></pre> Ruby master - Feature #12523 (Open): `Object#values_at`https://bugs.ruby-lang.org/issues/125232016-06-27T14:59:57Zsawa (Tsuyoshi Sawada)
<p>It might be convenient to have a method that returns multiple attributes of an object.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span>
<span class="n">attr_accessors</span> <span class="ss">:foo</span><span class="p">,</span> <span class="ss">:bar</span><span class="p">,</span> <span class="ss">:baz</span>
<span class="k">def</span> <span class="nf">initialize</span> <span class="n">foo</span><span class="p">,</span> <span class="n">bar</span><span class="p">,</span> <span class="n">baz</span><span class="p">;</span> <span class="vi">@foo</span><span class="p">,</span> <span class="vi">@bar</span><span class="p">,</span> <span class="vi">@baz</span> <span class="o">=</span> <span class="n">foo</span><span class="p">,</span> <span class="n">bar</span><span class="p">,</span> <span class="n">baz</span> <span class="k">end</span>
<span class="k">end</span>
<span class="n">a</span> <span class="o">=</span> <span class="no">A</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"b"</span><span class="p">,</span> <span class="s2">"c"</span><span class="p">)</span>
<span class="n">a</span><span class="p">.</span><span class="nf">values_at</span><span class="p">(</span><span class="ss">:baz</span><span class="p">,</span> <span class="ss">:foo</span><span class="p">)</span> <span class="c1"># => ["c", "a"]</span>
</code></pre> Ruby master - Feature #12319 (Open): `Module#const_get` does not accept symbol with nested namehttps://bugs.ruby-lang.org/issues/123192016-04-26T01:25:39Zsawa (Tsuyoshi Sawada)
<p><code>Module#const_get</code> accepts non-nested string, nested string, and non-nested symbol:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span><span class="p">;</span> <span class="k">class</span> <span class="nc">B</span><span class="p">;</span> <span class="k">class</span> <span class="nc">C</span> <span class="k">end</span> <span class="k">end</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">const_get</span><span class="p">(</span><span class="s2">"B"</span><span class="p">)</span> <span class="c1"># => A::B</span>
<span class="no">A</span><span class="p">.</span><span class="nf">const_get</span><span class="p">(</span><span class="s2">"B::C"</span><span class="p">)</span> <span class="c1"># => A::B::C</span>
<span class="no">A</span><span class="p">.</span><span class="nf">const_get</span><span class="p">(</span><span class="ss">:B</span><span class="p">)</span> <span class="c1"># => A::B</span>
</code></pre>
<p>but does not accept nested symbol:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span><span class="p">.</span><span class="nf">const_get</span><span class="p">(</span><span class="ss">:"B::C"</span><span class="p">)</span> <span class="c1"># => NameError: wrong constant name B::C</span>
</code></pre>
<p>I would like this to be made possible.</p> Ruby master - Feature #12145 (Open): Aliashood between `size` and `length` is not consistenthttps://bugs.ruby-lang.org/issues/121452016-03-05T19:12:01Zsawa (Tsuyoshi Sawada)
<p>When <code>size</code> and <code>length</code> have the same implementation, depending on the class, they are either independently defined methods, or the former is an alias of the latter. Particularly for <code>Array</code>:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="p">[].</span><span class="nf">method</span><span class="p">(</span><span class="ss">:size</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :length</span>
<span class="p">[].</span><span class="nf">method</span><span class="p">(</span><span class="ss">:length</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :length</span>
</code></pre>
<p>but for <code>Hash</code>, <code>String</code>, and <code>Symbol</code>:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="p">{}.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:size</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :size</span>
<span class="p">{}.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:length</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :length</span>
<span class="s2">""</span><span class="p">.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:size</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :size</span>
<span class="s2">""</span><span class="p">.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:length</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :length</span>
<span class="ss">:""</span><span class="p">.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:size</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :size</span>
<span class="ss">:""</span><span class="p">.</span><span class="nf">method</span><span class="p">(</span><span class="ss">:length</span><span class="p">).</span><span class="nf">original_name</span> <span class="c1"># => :length</span>
</code></pre>
<p>This might be a big issue, but since there is a standard Ruby method <code>original_name</code>, which returns different results, whether this being one way or another should matter. And I see no reason why they should behave differently. They should be unified in one way. Perhaps <code>Hash</code>, <code>String</code>, and <code>Symbol</code> should be made in the same way as with <code>Array</code>.</p> Ruby master - Feature #12096 (Closed): New notation for instance variables and class variableshttps://bugs.ruby-lang.org/issues/120962016-02-21T15:09:45Zsawa (Tsuyoshi Sawada)
<p>In order to create symbols that include non-word characters, we have the <code>:'...'</code> notation:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="ss">:'foo-bar'</span>
<span class="ss">:"foo-bar"</span>
</code></pre>
<p>What about extending this notation to instance variables and class variables? The use case is to solve the problems raised in <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Allow attr_reader :foo? to define instance method foo? for accessing @foo (Rejected)" href="https://bugs.ruby-lang.org/issues/12046">#12046</a>, <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: Allow an attr_ variant for query-methods that end with a question mark '?' character, such as: d... (Rejected)" href="https://bugs.ruby-lang.org/issues/11167">#11167</a>, <a class="issue tracker-2 status-6 priority-4 priority-default closed" title="Feature: A proposal for something like: attr_reader :foo? - with the trailing '?' question mark (Rejected)" href="https://bugs.ruby-lang.org/issues/10720">#10720</a>. There, the problem was that, even though we can have methods like <code>foo?</code> or symbols like <code>:foo?</code>, we cannot have corresponding instance variables. My proposal is to introduce a similar notation for instance variables:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="err">@</span><span class="s1">'foo?'</span>
<span class="err">@</span><span class="s2">"foo?"</span>
</code></pre>
<p>I can't think of a similar use case for class variables, but there is no reason to make class variables to behave different from instance variables more than necessary, so there can also be the corresponding notation for class variables:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="err">@@</span><span class="s1">'foo?'</span>
<span class="err">@@</span><span class="s2">"foo?"</span>
</code></pre>
<p>Right now, these notations raise syntax errors, so I don't think it conflicts (raises ambiguity) with the existing syntax.</p> Ruby master - Bug #12090 (Closed): `Range#cover` does not raise an exception when comparison failshttps://bugs.ruby-lang.org/issues/120902016-02-19T15:37:32Zsawa (Tsuyoshi Sawada)
<p>The documentation for <code>Range#cover?</code> says,</p>
<pre><code>cover?(obj) → true or false
Returns true if obj is between the begin and end of the range.
This tests begin <= obj <= end when exclude_end? is false and begin <= obj < end when exclude_end? is true.
</code></pre>
<p>which implies that, when comparison fails, <code>cover?</code> should raise an error. But actually, it doesn't:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="s2">"a"</span> <span class="o"><=</span> <span class="mi">1</span> <span class="c1"># => ArgumentError: comparison of String with 1 failed</span>
<span class="mi">1</span> <span class="o"><=</span> <span class="s2">"a"</span> <span class="c1"># => ArgumentError: comparison of Fixnum with String failed</span>
<span class="p">(</span><span class="s2">"a"</span><span class="o">..</span><span class="s2">"z"</span><span class="p">).</span><span class="nf">cover?</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="c1"># => false</span>
</code></pre>
<p>It silently returns <code>false</code> instead of raising an error.</p>
<p>Either <code>Range#cover?</code> should raise an error when comparison fails, or the documentation should be changed to correctly describe this behaviour.</p> Ruby master - Feature #12084 (Closed): `Class#instance`https://bugs.ruby-lang.org/issues/120842016-02-18T09:31:05Zsawa (Tsuyoshi Sawada)
<p>For meta-programming/debugging purposes, I would like to request the inverse of <code>Object#singleton_class</code>. Namely, a method that is called on a class that is a singleton class, and returns the object it is a singleton of. Since the <code>Singleton</code> module in the standard library <a href="http://ruby-doc.org/stdlib-2.3.0/libdoc/singleton/rdoc/Singleton.html" class="external">http://ruby-doc.org/stdlib-2.3.0/libdoc/singleton/rdoc/Singleton.html</a> assigns the method name <code>instance</code> to such classes, I think <code>Class#instance</code> should be the name for such feature.</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="no">Array</span><span class="p">.</span><span class="nf">singleton_class</span><span class="p">.</span><span class="nf">instance</span> <span class="c1"># => Array</span>
<span class="s2">"foo"</span><span class="p">.</span><span class="nf">singleton_class</span><span class="p">.</span><span class="nf">instance</span> <span class="c1"># => "foo"</span>
</code></pre>
<p>When the receiver is a class but is not a singleton class, then it should raise an error.</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="no">Array</span><span class="p">.</span><span class="nf">instance</span> <span class="c1"># => error</span>
</code></pre> Ruby master - Feature #11927 (Open): Return value for `Module#include` and `Module#prepend`https://bugs.ruby-lang.org/issues/119272015-12-30T11:40:36Zsawa (Tsuyoshi Sawada)
<p>Currently, <code>Module#include</code> and <code>Module#prepend</code> return the receiver, regardless of whether the ancestor chain has been modified. It is not straightforward to know whether it actually had effect.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">include</span> <span class="no">B</span> <span class="c1"># => A</span>
<span class="no">A</span><span class="p">.</span><span class="nf">ancestors</span> <span class="c1"># => [A, B]</span>
<span class="no">A</span><span class="p">.</span><span class="nf">prepend</span> <span class="no">B</span> <span class="c1"># => A</span>
<span class="no">A</span><span class="p">.</span><span class="nf">ancestors</span> <span class="c1"># => [A, B]</span>
</code></pre>
<p>I propose that, when <code>Module#include</code> and <code>Module#prepend</code> have no effect, they should either:</p>
<p>(1) return <code>nil</code><br>
(2) return <code>false</code>, or<br>
(3) raise an exception</p>
<p>This is similar to <code>Kernel#require</code>, which returns <code>false</code> when it has no effect. To make it parallel with <code>Kernel#require</code>, it might be even better to return <code>true</code> when <code>Module#include</code> and <code>Module#prepend</code> have effect, and <code>false</code> otherwise. It makes no sense to return the receiver because that is known.</p>
<p>Some relevant cases with expectations are:</p>
<ul>
<li>prepend after include</li>
</ul>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">include</span> <span class="no">B</span> <span class="c1"># => A/true</span>
<span class="no">A</span><span class="p">.</span><span class="nf">prepend</span> <span class="no">B</span> <span class="c1"># => nil/false/exception</span>
</code></pre>
<ul>
<li>include after prepend</li>
</ul>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">prepend</span> <span class="no">B</span> <span class="c1"># => A/true</span>
<span class="no">A</span><span class="p">.</span><span class="nf">include</span> <span class="no">B</span> <span class="c1"># => nil/false/exception</span>
</code></pre>
<ul>
<li>include/prepend after include/include at superclass</li>
</ul>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">include</span> <span class="no">M</span> <span class="c1"># => A/true</span>
<span class="k">class</span> <span class="nc">B</span> <span class="o"><</span> <span class="no">A</span><span class="p">;</span> <span class="k">end</span>
<span class="no">B</span><span class="p">.</span><span class="nf">include</span> <span class="no">M</span> <span class="c1"># => nil/false/exception</span>
</code></pre> Ruby master - Feature #11919 (Rejected): Passing a module directly https://bugs.ruby-lang.org/issues/119192015-12-29T03:57:00Zsawa (Tsuyoshi Sawada)
<p>Refinement requires a named module:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">MyRefinement</span>
<span class="n">refine</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">end</span>
<span class="n">using</span> <span class="no">MyRefinement</span>
</code></pre>
<p>but often (but not always), refinements are called by the <code>using</code> command only in once in a single file, and should not need to be named in such case. Also, the purpose of refinement is to not pollute classes with methods. Necessity to define a module and polluting the name space looks to me to go against this idea.</p>
<p>I would like to do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">using</span> <span class="no">Module</span><span class="p">.</span><span class="nf">new</span> <span class="k">do</span>
<span class="n">refine</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">end</span>
</code></pre> Ruby master - Feature #11879 (Closed): `Module#prepended_modules`https://bugs.ruby-lang.org/issues/118792015-12-26T14:52:58Zsawa (Tsuyoshi Sawada)
<p><code>Module#included_modules</code> include prepended modules:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">prepend</span> <span class="no">B</span>
<span class="no">A</span><span class="p">.</span><span class="nf">included_modules</span> <span class="c1"># => [B]</span>
</code></pre>
<p>This is confusing, and is not useful. I think prepended modules should not be included in <code>Module#included_modules</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span><span class="p">.</span><span class="nf">included_modules</span> <span class="c1"># => []</span>
</code></pre>
<p>I also propose that prepended modules should be included in a new method <code>Module#prepended_modules</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span><span class="p">.</span><span class="nf">prepended_modules</span> <span class="c1"># => [B]</span>
</code></pre> Ruby master - Bug #11878 (Rejected): Comparison of prepended moduleshttps://bugs.ruby-lang.org/issues/118782015-12-26T14:44:08Zsawa (Tsuyoshi Sawada)
<p>Including module <code>B</code> to class/module <code>A</code> gives the following results (as expected):</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">A</span><span class="p">;</span> <span class="k">end</span>
<span class="k">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">include</span> <span class="no">B</span>
<span class="no">A</span> <span class="o"><</span> <span class="no">B</span> <span class="c1"># => true</span>
<span class="no">B</span> <span class="o"><</span> <span class="no">A</span> <span class="c1"># => false</span>
<span class="no">A</span> <span class="o"><=></span> <span class="no">B</span> <span class="c1"># => -1</span>
</code></pre>
<p>And prepending module <code>C</code> to <code>A</code> gives the following results:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">module</span> <span class="nn">C</span><span class="p">;</span> <span class="k">end</span>
<span class="no">A</span><span class="p">.</span><span class="nf">prepend</span> <span class="no">C</span>
<span class="no">A</span> <span class="o"><</span> <span class="no">C</span> <span class="c1"># => true</span>
<span class="no">C</span> <span class="o"><</span> <span class="no">A</span> <span class="c1"># => nil</span>
<span class="no">A</span> <span class="o"><=></span> <span class="no">C</span> <span class="c1"># => -1</span>
</code></pre>
<p>It looks like including and prepending almost do not make difference with respect to module comparison, i.e., <code>A < B</code> and <code>A < C</code> are the same, and <code>A <=> B</code> and <code>A <=> C</code> are the same. However, then, the difference between <code>B < A</code> and <code>C < A</code> stands out unexplained. I suppose this is a bug. If <code>C < A</code> were to return <code>false</code>, then it would be at least consistent.</p>
<p>However, if that was what was intended, then at least to me, it is strange. In that case, I would like to make this a feature request. I would rather expect:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span> <span class="o"><</span> <span class="no">C</span> <span class="c1"># => false</span>
<span class="no">C</span> <span class="o"><</span> <span class="no">A</span> <span class="c1"># => true</span>
<span class="no">A</span> <span class="o"><=></span> <span class="no">C</span> <span class="c1"># => 1</span>
</code></pre> Ruby master - Bug #11860 (Closed): Double splat does not work on empty hash assigned via variablehttps://bugs.ruby-lang.org/issues/118602015-12-22T08:33:54Zsawa (Tsuyoshi Sawada)
<p>When an empty hash is given as a literal, the double splat operates on it, and leaves nothing, which is expected.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">String</span>
<span class="k">def</span> <span class="nf">foo</span><span class="p">;</span> <span class="k">end</span>
<span class="k">end</span>
<span class="p">[</span><span class="o">**</span><span class="p">{}]</span> <span class="c1"># => []</span>
<span class="s2">"foo"</span><span class="p">.</span><span class="nf">foo</span><span class="p">(</span><span class="o">**</span><span class="p">{})</span> <span class="c1"># => nil</span>
<span class="s2">"foo"</span><span class="p">.</span><span class="nf">send</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">,</span> <span class="o">**</span><span class="p">{})</span> <span class="c1"># => nil</span>
</code></pre>
<p>However, when an empty hash is given via variable, the double splat retains an empty hash in place.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">h</span> <span class="o">=</span> <span class="p">{}</span>
<span class="p">[</span><span class="o">**</span><span class="n">h</span><span class="p">]</span> <span class="c1"># => [{}]</span>
<span class="s2">"foo"</span><span class="p">.</span><span class="nf">foo</span><span class="p">(</span><span class="o">**</span><span class="n">h</span><span class="p">)</span> <span class="c1"># => wrong number of arguments (given 1, expected 0)</span>
<span class="s2">"foo"</span><span class="p">.</span><span class="nf">send</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">,</span> <span class="o">**</span><span class="n">h</span><span class="p">)</span> <span class="c1"># => wrong number of arguments (given 1, expected 0)</span>
</code></pre> Ruby master - Feature #11797 (Closed): `Enumerator#with_object` with multiple objectshttps://bugs.ruby-lang.org/issues/117972015-12-09T16:15:51Zsawa (Tsuyoshi Sawada)
<p>Sometimes, when working with <code>Enumerator#with_object</code>, I want to keep some additional temporary objects besides the one to return. A use case is as follows (I got this from this StackOverflow question: <a href="http://stackoverflow.com/questions/3418123" class="external">http://stackoverflow.com/questions/3418123</a>). Suppose I have an enumerator created from an array:</p>
<pre><code>e = ["a", "b", "c", "c", "a", "c"].to_enum
</code></pre>
<p>and want to get an array of its repeated elements in the order they are repeated (i.e., appears for the second time):</p>
<pre><code># => ["c", "a"]
</code></pre>
<p>I can do it using <code>Enumerator#with_object</code> like this:</p>
<pre><code>e.to_enum.with_object([{}, []]){|c, (h, a)| h[c] ? a.push(c) : h.store(c, true)}.last.uniq
</code></pre>
<p>Here, I am getting the array referred to as <code>a</code> in the block, but besides that, I am using a temporal hash <code>h</code>. I thought it would be nice if <code>Enumerator#with_object</code> accepts one or more objects, pass them individually as block arguments, and returns only the last argument so that I can do this:</p>
<pre><code>e.to_enum.with_object({}, []){|c, h, a| h[c] ? a.push(c) : h.store(c, true)}.uniq
</code></pre> Ruby master - Feature #11308 (Closed): Optional `include_super=true` parameter for `*method_defin...https://bugs.ruby-lang.org/issues/113082015-06-26T04:47:24Zsawa (Tsuyoshi Sawada)
<p>I request the following methods in the <code>Module</code> class:</p>
<ul>
<li><code>method_defined?</code></li>
<li><code>private_method_defined?</code></li>
<li><code>protected_method_defined?</code></li>
<li><code>public_method_defined?</code></li>
</ul>
<p>to take an optional <code>include_super</code> parameter with the default value <code>true</code>, and work similar to the methods:</p>
<ul>
<li><code>instance_methods</code></li>
<li><code>private_instance_methods</code></li>
<li><code>protected_instance_methods</code></li>
<li>and <code>public_instance_methods</code>
</li>
</ul> Ruby master - Feature #10880 (Rejected): Subclassing Array from Enumeratorhttps://bugs.ruby-lang.org/issues/108802015-02-21T20:04:33Zsawa (Tsuyoshi Sawada)
<p>It often happens that I want to use a method from the <code>Enumerator</code> class on an array, and so I frequently use <code>Array#to_enum</code>. Since <code>Array</code> and <code>Enumerator</code> share the same parent <code>Enumerable</code>, they should be very close. I think it would be convenient if <code>Array</code> inherits from <code>Enumerator</code>. (Perhaps the same thing can be said for <code>Hash</code> too)</p> Ruby master - Bug #10845 (Closed): Subclassing Stringhttps://bugs.ruby-lang.org/issues/108452015-02-10T23:41:25Zsawa (Tsuyoshi Sawada)
<p>If I make a subclass of <code>String</code>, the method <code>*</code> returns an instance of that class.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">MyString</span> <span class="o"><</span> <span class="no">String</span>
<span class="k">end</span>
<span class="no">MyString</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">).</span><span class="nf">*</span><span class="p">(</span><span class="mi">2</span><span class="p">).</span><span class="nf">class</span> <span class="c1">#=> MyString</span>
</code></pre>
<p>This is different from other similar operations like <code>+</code> and <code>%</code>, which return a <code>String</code> instance.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">MyString</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="s2">"foo"</span><span class="p">).</span><span class="nf">+</span><span class="p">(</span><span class="s2">"bar"</span><span class="p">).</span><span class="nf">class</span> <span class="c1">#=> String</span>
<span class="no">MyString</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="s2">"%{foo}"</span><span class="p">).</span><span class="nf">%</span><span class="p">(</span><span class="ss">foo: </span><span class="s2">"bar"</span><span class="p">).</span><span class="nf">class</span> <span class="c1">#=> String</span>
</code></pre>
<p>I don't see clear reason why <code>*</code> is to be different from <code>+</code> and <code>%</code>, and thought that perhaps either the behaviour with <code>*</code> is a bug, or the behaviour with <code>+</code> and <code>%</code> is a bug.</p>
<p>Or, is a reason why they are different?</p> Ruby master - Feature #10797 (Closed): `inherit` parameter for `..._defined?` methods in Modulehttps://bugs.ruby-lang.org/issues/107972015-01-28T22:27:49Zsawa (Tsuyoshi Sawada)
<p><code>Module#const_defined?</code> takes an optional argument <code>inherit</code> with default value <code>true</code> to control whether to consider inheritance. But the following methods do not:</p>
<ul>
<li><code>Module#method_defined?</code></li>
<li><code>Module#private_method_defined?</code></li>
<li><code>Module#protected_method_defined?</code></li>
<li><code>Module#public_method_defined?</code></li>
</ul>
<p>They only allow what would correspond to <code>inherit = true</code>. I request an optional argument <code>inherit</code> with default value <code>true</code> to be added to these methods to control whether inheritance should be considered.</p> Ruby master - Feature #10771 (Closed): An easy way to get the source location of a constanthttps://bugs.ruby-lang.org/issues/107712015-01-22T05:50:18Zsawa (Tsuyoshi Sawada)
<p>For constants, it is difficult to get the source location where it was (last) defined. I request either of the following to be implemented:</p>
<ul>
<li>
<p>Tracepoint emits a signal when a constant is defined.</p>
</li>
<li>
<p>Implement a <code>Constant</code> class (similar to <code>Method</code> class) and a <code>constant</code> method (similar to <code>method</code> method) that behave as follows:</p>
<pre><code> foo1.rb
1| module Foo
2| Bar = :bar
3| end
4| Foo.constant(:Bar) #=> #<Constant: Foo#Bar>
5| Foo.constant(:Bar).source_location #=> ["foo1.rb", 2]
</code></pre>
</li>
<li>
<p>Implement <code>Module#constant_source_location</code></p>
<pre><code> foo2.rb
1| module Foo
2| Bar = :bar
3| end
4| Foo.constant_source_location(:Bar) #=> ["foo2.rb", 2]
</code></pre>
</li>
</ul> Ruby master - Feature #10463 (Rejected): :~@ and :!@ are not parsed correctlyhttps://bugs.ruby-lang.org/issues/104632014-11-01T02:13:11Zsawa (Tsuyoshi Sawada)
<p>The at mark in literal symbols <code>:~@</code> and <code>:!@</code> are ignored.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="ss">:~</span><span class="err">@</span> <span class="c1"># => :~</span>
<span class="p">:</span><span class="o">!</span><span class="err">@</span> <span class="c1"># => :!</span>
</code></pre> Ruby master - Bug #10422 (Closed): RDoc for BasicObject has methods that do not existhttps://bugs.ruby-lang.org/issues/104222014-10-23T07:44:37Zsawa (Tsuyoshi Sawada)
<p>RDoc for BasicObject (<a href="http://www.ruby-doc.org/core-2.1.3/BasicObject.html" class="external">http://www.ruby-doc.org/core-2.1.3/BasicObject.html</a>) has descriptions for methods <code>object_id</code> and <code>send</code>, which do not exist. Also, <code>send</code> and <code>__send__</code> are listed twice.</p> Ruby master - Feature #10394 (Feedback): An instance method on Enumerator that evaluates the bloc...https://bugs.ruby-lang.org/issues/103942014-10-16T14:23:15Zsawa (Tsuyoshi Sawada)
<p><strong>Background</strong></p>
<p>There has been desire to omit the <code>| |</code> and the explicit receiver in a block used with an enumerator or an enumerable. Currently, when the content of the block is a single method that takes no argument, symbol-to-proc is used with the <code>&</code> syntax so that:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">].</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">s</span><span class="o">|</span> <span class="n">s</span><span class="p">.</span><span class="nf">upcase</span><span class="p">}</span>
</code></pre>
<p>can be written as:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">].</span><span class="nf">map</span><span class="p">(</span><span class="o">&</span><span class="ss">:upcase</span><span class="p">)</span>
</code></pre>
<p>There has repeated been proposals (<a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: map/collect extension which handles arguments (Open)" href="https://bugs.ruby-lang.org/issues/8987">#8987</a>, <a class="issue tracker-2 status-7 priority-4 priority-default closed" title="Feature: New one-argument block syntax: &. (Feedback)" href="https://bugs.ruby-lang.org/issues/9076">#9076</a>, <a class="issue tracker-2 status-1 priority-4 priority-default" title="Feature: [PATCH 0/n] Let underscore be positionally matched arg to omit binding obvious variable. (Open)" href="https://bugs.ruby-lang.org/issues/10318">#10318</a>) that express this desire to do this even when the block involves a method chain or a method with arguments like the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">].</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">s</span><span class="o">|</span> <span class="n">s</span><span class="p">.</span><span class="nf">concat</span><span class="p">(</span><span class="s2">"ber"</span><span class="p">)}</span>
<span class="p">[</span><span class="s2">" foo "</span><span class="p">,</span> <span class="s2">"</span><span class="se">\t</span><span class="s2">bar</span><span class="se">\n</span><span class="s2">"</span><span class="p">].</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">s</span><span class="o">|</span> <span class="n">s</span><span class="p">.</span><span class="nf">strip</span><span class="p">.</span><span class="nf">upcase</span><span class="p">}</span>
</code></pre>
<p>Focus has been on modifying how a block is passed to the enumerable/enumerator, and there has not been consensus on how the syntax should be.</p>
<p><strong>Proposal</strong></p>
<p>Unlike the earlier proposals, I suggest that there should be an instance method on <code>Enumerator</code>, let's say <code>Enumerator#as_self</code>, that evaluates the block each time with <code>self</code> being the block variable that would be passed otherwise. With such method, the cases above would be written like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="s2">"foo"</span><span class="p">,</span> <span class="s2">"bar"</span><span class="p">].</span><span class="nf">map</span><span class="p">.</span><span class="nf">as_self</span><span class="p">{</span><span class="n">concat</span><span class="p">(</span><span class="s2">"ber"</span><span class="p">)}</span>
<span class="p">[</span><span class="s2">" foo "</span><span class="p">,</span> <span class="s2">"</span><span class="se">\t</span><span class="s2">bar</span><span class="se">\n</span><span class="s2">"</span><span class="p">].</span><span class="nf">map</span><span class="p">.</span><span class="nf">as_self</span><span class="p">{</span><span class="n">strip</span><span class="p">.</span><span class="nf">upcase</span><span class="p">}</span>
</code></pre>
<p>This adds no modification to the syntax, it just requires a new method <code>Enumerator#as_self</code> to be implemented. I consider this method being along the lines of <code>Enumerator#with_index</code>, <code>Enumerator#with_object</code>; it intervenes between an enumerator (related to a block-taking method) and a block, and let the block-taking method work in a modified way.</p>
<p>It resembles <code>instance_eval</code>, but is different in that it assigns to <code>self</code> what would be a block variable (which changes for each iteration), instead of assigning the receiver.</p> Ruby master - Feature #10343 (Rejected): Postfix notations for `when` and `else` inside `case` st...https://bugs.ruby-lang.org/issues/103432014-10-08T16:42:45Zsawa (Tsuyoshi Sawada)
<p>In a <code>case</code> statement, the condition part (<code>when ...</code>) in the branches do not have the same length in general, and especially, <code>else</code> is much shorter than the conditions. So when we write the condition and the return value in a single line, they are not aligned, and are hard to read.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">case</span> <span class="n">foo</span>
<span class="k">when</span> <span class="n">some_very_long_proc</span> <span class="k">then</span> <span class="s2">"a"</span>
<span class="k">when</span> <span class="n">short_regex</span> <span class="k">then</span> <span class="s2">"bbb"</span>
<span class="k">when</span> <span class="n">some_long_regex</span> <span class="k">then</span> <span class="s2">"cc"</span>
<span class="k">else</span> <span class="s2">"dddd"</span>
<span class="k">end</span>
</code></pre>
<p>I propose to allow postfix notations with <code>when</code> and <code>else</code> (or <code>otherwise</code>) inside <code>case</code> statement as below:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">case</span> <span class="n">foo</span>
<span class="s2">"a"</span> <span class="k">when</span> <span class="n">some_very_long_proc</span>
<span class="s2">"bbb"</span> <span class="k">when</span> <span class="n">short_regex</span>
<span class="s2">"cc"</span> <span class="k">when</span> <span class="n">some_long_regex</span>
<span class="s2">"dddd"</span> <span class="k">else</span>
<span class="k">end</span>
</code></pre>
<p>Pros are:</p>
<ol>
<li>
<p>Postfix notation does not require <code>then</code> or <code>;</code>, so it is concise.</p>
</li>
<li>
<p>The return values from the branches (e.g., <code>"a"</code>, <code>"bb"</code>, <code>"ccc"</code>, <code>"dddd"</code>) tend to be shorter and more uniformly lengthened than the conditions, hence they are somewhat close to being aligned naturally, making this easier to read.</p>
</li>
<li>
<p>We are usually more interested in the return value than the condition of a branch, especially when we are reading someone's code and are trying to grasp what the <code>case</code> statement does or returns.</p>
</li>
<li>
<p>This notation is closer to case-like conditional notations regularly used in mathematics:</p>
<pre><code> ┌ 1 (x = 0)
x! = ┤
└ x (x - 1)! (otherwise)
</code></pre>
<p>So it would be easier to read for those who are familiar with mathematics.</p>
</li>
</ol> Ruby master - Feature #10240 (Rejected): `String#to_a`https://bugs.ruby-lang.org/issues/102402014-09-14T14:51:38Zsawa (Tsuyoshi Sawada)
<p>I often want to exclude the empty strings from an array of strings. A use case is to join an array of strings with <code>", "</code>, removing the empty ones, as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="s2">"Foo"</span><span class="p">,</span> <span class="s2">""</span><span class="p">,</span> <span class="s2">"Bar"</span><span class="p">].</span><span class="nf">reject</span><span class="p">(</span><span class="o">&</span><span class="ss">:empty?</span><span class="p">).</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">)</span> <span class="c1"># => "Foo, Bar"</span>
</code></pre>
<p>In a similar situation with arrays of arrays, the empty ones can be excluded by using <code>*</code> and <code>Array#to_a</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="o">*</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="o">*</span><span class="p">[],</span> <span class="o">*</span><span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">]]</span> <span class="c1"># => [1, 2, 3, 4]</span>
</code></pre>
<p>I would like to propose <code>String#to_a</code> defined as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">String</span>
<span class="k">def</span> <span class="nf">to_a</span><span class="p">;</span> <span class="n">empty?</span> <span class="p">?</span> <span class="p">[]</span> <span class="p">:</span> <span class="p">[</span><span class="nb">self</span><span class="p">]</span> <span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>Then we can do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="o">*</span><span class="s2">"Foo"</span><span class="p">,</span> <span class="o">*</span><span class="s2">""</span><span class="p">,</span> <span class="o">*</span><span class="s2">"Bar"</span><span class="p">].</span><span class="nf">join</span><span class="p">(</span><span class="s2">", "</span><span class="p">)</span>
</code></pre> Ruby master - Bug #10184 (Closed): irb terminates with no method errorhttps://bugs.ruby-lang.org/issues/101842014-08-29T16:33:54Zsawa (Tsuyoshi Sawada)
<p>When I input the following lines in irb, the irb terminates.</p>
<pre><code>$ irb
irb(main):001:0> def !; end
=> :!
irb(main):002:0> !
/usr/local/lib/ruby/2.1.0/irb/input-method.rb:153:in `gets': private method `!' called for false:FalseClass (NoMethodError)
...
$
</code></pre>
<p>A corresponding question is posted on StackOverflow at <a href="http://stackoverflow.com/questions/25572126/irb-terminates-with-no-method-error/25572313#25572313" class="external">http://stackoverflow.com/questions/25572126/irb-terminates-with-no-method-error/25572313#25572313</a>.</p> Ruby master - Feature #10118 (Closed): Double splat for non-symbol keyshttps://bugs.ruby-lang.org/issues/101182014-08-07T23:45:13Zsawa (Tsuyoshi Sawada)
<p>The double splat operator ** only seems to work with hashes whose keys are symbols. It will not work when a key is a string, for example. This is true for both ways; for construction:</p>
<pre><code>def foo **; end
foo(:a => 3) #=> nil
foo("a" => 3) #=> ArgumentError: wrong number of arguments (1 for 0)
</code></pre>
<p>and destruction:</p>
<pre><code>def bar *; end
bar(**{:a => 3}) #=> nil
bar(**{"a" => 3}) #=> TypeError: wrong argument type String (expected Symbol)
</code></pre>
<p>This is confusing. I propose that the double splat syntax should be extended so that it works even when the keys are not symbols.</p> Ruby master - Feature #9948 (Closed): Safely insert an object into an arrayhttps://bugs.ruby-lang.org/issues/99482014-06-17T00:40:48Zsawa (Tsuyoshi Sawada)
<p>When I insert an object using <code>Array#insert(index, object)</code> method (or <code>Array#[index]= object</code>), it happened sometimes that I mistakenly passed <code>index</code> that is too big, and too often in such cases was the bug very difficult to detect because in such case, <code>insert</code> will silently insert <code>nil</code> to fill up the empty slots:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="ss">:foo</span><span class="p">,</span> <span class="ss">:bar</span><span class="p">].</span><span class="nf">insert</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="ss">:baz</span><span class="p">)</span> <span class="c1"># => [:foo, :bar, nil, nil, :baz]</span>
</code></pre>
<p>On the other hand, when the index is too small (negative), <code>index</code> raises an index error. I wish that an error were raised when the index is too big (when <code>index</code> is greater than <code>length</code> of <code>self</code>), but it is perhaps a bad idea to change the feature of <code>insert</code> by now. So I propose that a new method being added, something like <code>Array#safely_insert</code>, which works the same as <code>insert</code>, except that when <code>index</code> is larger than the size of the array, it should raise:</p>
<pre><code>Index Error: index #{indexs} too large for array; maximum: #{length}
</code></pre> Ruby master - Feature #9602 (Feedback): Logic with `Enumerable#grep`https://bugs.ruby-lang.org/issues/96022014-03-06T10:36:45Zsawa (Tsuyoshi Sawada)
<p><code>Enumerable#grep</code> is useful to filter things:</p>
<pre><code>[nil, {}, [], 1, :foo, "foo"].grep(String)
# => ["foo"]
</code></pre>
<ol>
<li>
<p>Often, the condition cannot be expressed as a single object on which <code>===</code> is applied, but as a disjunction over <code>===</code> applied to multiple objects. I would like <code>Enumerable#grep</code> to take arbitrary number of arguments, and when they are more than one, a logical disjunction applies, just as when there are multiple comma-separated objects after <code>when</code> in <code>case</code> condition:</p>
<pre><code> [nil, {}, [], 1, :foo, "foo"].grep(String, Symbol, Array)
# => [[], :foo, "foo"]
</code></pre>
</li>
<li>
<p>Also, it often happens that I want the negation of grep. Perhaps, <code>Enumerable#grepv</code> (<code>grepv</code> comes from <code>grep -v</code>) can be implemented as negation of <code>Enumerable#grep</code>, i.e., select elements for which <code>===</code> returns false on any of the arguments:</p>
<pre><code> [nil, {}, [], 1, :foo, "foo"].grepv(String, Symbol, Array)
# => [nil, {}, 1]
</code></pre>
</li>
</ol> Ruby master - Feature #9587 (Closed): Integer#times with optional starting valuehttps://bugs.ruby-lang.org/issues/95872014-03-02T19:52:38Zsawa (Tsuyoshi Sawada)
<p>Just like <code>Enumerator#with_index</code> takes an optional argument that specifies the initial value of the index, I would like to request that <code>Integer#times</code> take an optional argument that specifies the initial value. The usefulness of it is similar to that of <code>with_index</code> taking an argument. We sometimes want to repeat tasks a given number of times, and want to use an index not necessarily starting from <code>0</code>.</p>
<pre><code>6.times(1){|i| puts "Chapter #{i}"}
</code></pre>
<p>should give</p>
<pre><code>Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
</code></pre>
<p>with the return value <code>6</code>. We can do it with <code>1.upto(6)</code>, or with <code>#{i + 1}</code> within the block, but giving the initial value to <code>times</code> is much easier.</p> Ruby master - Feature #9515 (Open): `IO.each` and `CSV.each`https://bugs.ruby-lang.org/issues/95152014-02-12T16:16:41Zsawa (Tsuyoshi Sawada)
<p>In <code>IO</code> class, there are pairs of a class method and an instance method with related function:</p>
<ul>
<li>
<code>IO.read</code> and <code>IO#read</code>
</li>
<li>
<code>IO.write</code> and <code>IO#write</code>
</li>
<li>
<code>IO.foreach</code> and <code>IO#each</code> (or its alias <code>IO#each_line</code>)</li>
</ul>
<p>For consistency, please make <code>IO.each</code> an alias for <code>IO.foreach</code>.</p>
<p>The same thing can be said for <code>CSV.each</code>.</p> Ruby master - Feature #9037 (Closed): Memoization of "anonymous constants"https://bugs.ruby-lang.org/issues/90372013-10-20T15:51:19Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
I was thinking about the frozen literal argument in <a href="https://bugs.ruby-lang.org/issues/8992" class="external">https://bugs.ruby-lang.org/issues/8992</a>. I believe that the original intent for that proposal was to avoid reevaluation of specially marked string literals. I think that that idea would be best realized by memoization of a literal rather than freezing. Suppose we introduce a method <code>memoize</code> like this:</p>
<pre><code>memoize{"foo"}
</code></pre>
<p>whose block would be evaluated only the first this expression it is parsed, and always returns the return value of the block, then that would suffice for the purpose. In fact, this proposal in an extension/generalization of the arguments regarding frozen array/hash literals. The proposed syntax allows objects of an arbitrary class to be memoized, and is regardless of whether it is a literal expression. It is also independent of and is free from the difficulties regarding what to do with frozen arrays/hashes.</p>
<p>At the Ruby level, I believe there is a way to implement this by keeping a hash whose key would be something that uniquely identifies the source location of this expression. But I also believe there must be a better way at the C level.</p>
<p>If it is possible to add a keyword to the syntax, then we can have <code>memoize</code> as a keyword (of the kind similar to <code>defined?</code>) instead of a method, used like:</p>
<pre><code>memoize("foo")
</code></pre>
<p>or</p>
<pre><code>memoize "foo"
</code></pre>
<p>which might look more pleasant.</p>
<p>In either case, for Ruby 2.0 compatibility, a method <code>memoize</code> can be defined to evaluate the block or return the argument.</p>
<p>=end</p> Ruby master - Feature #8970 (Open): Array.zip and Array.producthttps://bugs.ruby-lang.org/issues/89702013-10-01T03:57:09Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
Most of the time when I use <code>Array#zip</code> or <code>Array#product</code>, I feel cumbursome that I have to take out the first array and pass it as a receiver. For example, if I have</p>
<pre><code>a = [[:a, :b, :c], [:d, :e, :f], [:g, :h, :i]]
</code></pre>
<p>I have to do something like this:</p>
<pre><code>a.first.zip(*a.drop(1)){...}
a.first.product(*a.drop(1)){...}
</code></pre>
<p>Sometimes, the receiver (i.e., the first array) has significance, but most other times, that breaks asymmetry, making the code look ugly.</p>
<p>I would be happy if we had <code>Array.zip</code> and <code>Array.product</code> in addition so that we can do it like this:</p>
<pre><code>Array.zip(*a){...}
Array.product(*a){...}
</code></pre>
<p>=end</p> Ruby master - Feature #8948 (Assigned): Frozen regexhttps://bugs.ruby-lang.org/issues/89482013-09-25T04:02:37Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
I see that frozen string was accepted for Ruby 2.1, and frozen array and hash are proposed in <a href="https://bugs.ruby-lang.org/issues/8909" class="external">https://bugs.ruby-lang.org/issues/8909</a>. I feel there is even more use case for a frozen regex, i.e., a regex literal that generates a regex only once. It is frequent to have a regex within a frequently repeated portion of code, and generating the same regex each time is a waste of resource. At the moment, we can have a code like:</p>
<pre><code>class Foo
RE1 = /pattern1/
RE2 = /pattern1/
RE3 = /pattern1/
def classify
case self
when RE1 then 1
when RE2 then 2
when RE3 then 3
else 4
end
end
end
</code></pre>
<p>but suppose we have a frozen <code>Regexp</code> literal <code>//f</code>. Then we can write like:</p>
<pre><code>class Foo
def classify
case self
when /pattern1/f then 1
when /pattern1/f then 2
when /pattern1/f then 3
else 4
end
end
end
</code></pre>
<p>=end</p> Ruby master - Feature #8834 (Open): Kernel#load_relativehttps://bugs.ruby-lang.org/issues/88342013-08-30T10:32:44Zsawa (Tsuyoshi Sawada)
<p>The intended difference between <code>Kernel#require</code> and <code>Kernel#load</code> is that the former is for external libraries and the latter is for Ruby scripts internal to the project. Considering this fact, <code>load</code> should be more likely than <code>require</code> to be used in a situation where you want to call a file through a relative path. Strangely, there is <code>Kernel#require_relative</code>, but no <code>Kernel#load_relative</code>. I request <code>Kernel#load_relative</code>. It is even more necessary than <code>Kernel#require_relative</code>.</p>
<p>It seems to me that people are using <code>Kernel#require_relative</code> when they want to use a relative path, even in the context where they are supposed to use <code>load</code> because of the lack of <code>Kernel#load_relative</code>. I don't think this is a good practice. Furthermore, in cases where you have a file without a <code>.rb</code> or other extention that you want to call via a relative path, there is no good way to do it.</p> Ruby master - Feature #8827 (Closed): A method that flips the receiver and the first argumenthttps://bugs.ruby-lang.org/issues/88272013-08-28T13:18:27Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
If it often happens that we need to pass to a method an argument that is the result of a long chain of operations:</p>
<pre><code>Hash[some_chain_of_operations_that_ends_up_with_an_array]
File.read(some_chain_of_operations_that_ends_up_with_a_string)
YAML.dump(some_chain_of_operations_that_ends_up_with_an_object)
...
</code></pre>
<p>I believe one basic tenet of Ruby is to encourage method chaining, but that practice is discouraged in the examples above. It would be convenient if there is a method (let us call this <code>Object#flip</code>) that flips the receiver and the first argument and sends the method so that the examples above can be written as follows:</p>
<pre><code>some_chain_of_operations_that_ends_up_with_an_array.flip(Hash, :[])
some_chain_of_operations_that_ends_up_with_a_string.flip(File, :read)
some_chain_of_operations_that_ends_up_with_an_object.flip(YAML, :dump)
...
</code></pre>
<p>The implementation in Ruby may be as follows:</p>
<pre><code>class Object
def flip receiver, method, *rest, &pr
receiver.send(method, self, *rest, &pr)
end
end
</code></pre>
<p>It would be good if we can have that as a built-in Ruby method.</p>
<p>=end</p> Ruby master - Feature #8172 (Feedback): IndexError-returning counterparts to destructive Array me...https://bugs.ruby-lang.org/issues/81722013-03-27T10:51:46Zsawa (Tsuyoshi Sawada)
<p>There are a few desctructive <code>Array</code> methods that take an index as an argument and silently insert <code>nil</code> if the index is out of range:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[];</span> <span class="n">a</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="ss">:foo</span><span class="p">;</span> <span class="n">a</span> <span class="c1"># => [nil, :foo]</span>
<span class="p">[].</span><span class="nf">insert</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="ss">:foo</span><span class="p">)</span> <span class="c1"># => [nil, :foo]</span>
<span class="p">[].</span><span class="nf">fill</span><span class="p">(</span><span class="ss">:foo</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="c1"># => [nil, :foo]</span>
</code></pre>
<p>Among them, <code>Array#[]</code> has a counterpart that returns an <code>IndexError</code> when the index is out of range:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[].</span><span class="nf">fetch</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="c1"># => IndexError</span>
</code></pre>
<p>and this is useful to avoid bugs that would be difficult to find if <code>Array#[]</code> were used. However for <code>Array#insert</code> and <code>Array#fill</code>, there are no such counterparts, and that fact that these methods silently insert <code>nil</code> is often the cause of a bug that is difficult to find.</p>
<p>I suggest there should be some versions of these methods that return <code>IndexError</code> when index is out of range:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[].</span><span class="nf">insert!</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="ss">:foo</span><span class="p">)</span> <span class="c1"># => IndexError</span>
<span class="p">[].</span><span class="nf">fill!</span><span class="p">(</span><span class="ss">:foo</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="c1"># => IndexError</span>
</code></pre>
<p>I believe this would make debugging easier.</p> Ruby master - Feature #7639 (Closed): More freedom for location of commentshttps://bugs.ruby-lang.org/issues/76392012-12-31T02:29:31Zsawa (Tsuyoshi Sawada)
<p>When we chain methods with the period at the end of each line, we can put comments in between the lines:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span><span class="o">.</span>
<span class="c1"># First, we do blah blah</span>
<span class="n">method1</span><span class="o">.</span>
<span class="c1"># Second, we do blah blah</span>
<span class="n">method2</span><span class="p">.</span>
<span class="nf">=</span><span class="k">begin</span>
<span class="no">Third</span><span class="p">,</span> <span class="n">the</span> <span class="n">following</span> <span class="n">line</span>
<span class="n">does</span> <span class="n">this</span>
<span class="ow">and</span> <span class="n">that</span> <span class="o">...</span>
<span class="o">=</span><span class="k">end</span>
<span class="n">method3</span>
</code></pre>
<p>but when we have the period at the beginning of the line, putting comments in similar positions returns an error:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]</span>
<span class="c1"># First, we do blah blah</span>
<span class="p">.</span><span class="nf">method1</span>
<span class="c1"># Second, we do blah blah</span>
<span class="p">.</span><span class="nf">method2</span>
<span class="cm">=begin
Third, the following line
does this
and that ...
=end</span>
<span class="p">.</span><span class="nf">method3</span>
<span class="c1"># => Error</span>
</code></pre>
<p>It is confusing that putting comments between lines in a method chain is sometimes allowed and sometimes not. I think it would be convenient if comments are allowed in these positions even when the following line starts with a period, and I request this as a feature. Currently, it returns an error, which means that, if such syntax were allowed, there would be no conflict with the existing syntax.</p>
<p>Furthermore, putting the period at the beginning of a line is suited for method chains because the period will visually work as bullets, and it makes more sense to have comments right before those lines.</p> Ruby master - Feature #5735 (Closed): Extending the use of splat operator to when it is inside a ...https://bugs.ruby-lang.org/issues/57352011-12-09T13:31:02Zsawa (Tsuyoshi Sawada)
<p>Ruby convention of allowing omittion of the curly brackets for the last argument is convenient:</p>
<p>foo(arg1, arg2, 1 => :a, 2 => :b)</p>
<p>Sometimes, I want to pass a hash with some modifications. For example, suppose <code>h = {3 => :c, 4 => :d, 5 => :e}</code> is a hash already defined and that I want to add some key-value pairs as well as overwrite some values of <code>h</code>, such as {3 => :c, 4 => :f, 5 => :e, 6 => :g}, and pass that. The current convention only allows:</p>
<p>foo(arg1, arg2, h.merge(4 => :f, 6 => :g))</p>
<p>but it would be more convenient if a hash preceded by the splat operator is placed in a hash, it is interpreted as part of the hash, allowing notations like:</p>
<p>foo(arg1, arg2, *h, 4 => :f, 6 => :g)</p>
<p>or, if I want to overwrite the hash <code>{4 => :f, 6 => :g}</code> with <code>h</code>, then:</p>
<p>foo(arg1, arg2, 4 => :f, 6 => :g, *h)</p>
<p>Or besides the argument position, in general, usages like the following:</p>
<p>{3 => :h, *h, 4 => :f, 6 => :g}</p>
<p>This is an analogy from the splat operator used within an array:</p>
<p>[1, 2, *[4, 5, 6], 7, 8]</p>