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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 #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 - 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 - 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 #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 - 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 - 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 - 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 #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 - 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 - 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 - 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 #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 #15143 (Closed): Extend `Enumerable#to_h`https://bugs.ruby-lang.org/issues/151432018-09-20T02:23:27Zsawa (Tsuyoshi Sawada)
<p>Often, we call <code>Array#to_h</code> to the result of <code>Enumerable#map</code>:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">(</span><span class="mi">1</span><span class="o">..</span><span class="mi">5</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="p">[</span><span class="n">x</span><span class="p">,</span> <span class="n">x</span> <span class="o">**</span> <span class="mi">2</span><span class="p">]}.</span><span class="nf">to_h</span>
<span class="c1">#=> {1=>1, 2=>4, 3=>9, 4=>16, 5=>25}</span>
</code></pre>
<p>I am thinking of a feature to do this in a single method call.</p>
<p>Currently, <code>Enumerable#to_h</code> does not accept a block. I propose that, when <code>Enumerable#to_h</code> is called with a block (that has a subarray representing a key-value pair), return a hash that would be returned by applying the block to <code>map</code>, and <code>to_h</code> to the result:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">(</span><span class="mi">1</span><span class="o">..</span><span class="mi">5</span><span class="p">).</span><span class="nf">to_h</span><span class="p">{</span><span class="o">|</span><span class="n">x</span><span class="o">|</span> <span class="p">[</span><span class="n">x</span><span class="p">,</span> <span class="n">x</span> <span class="o">**</span> <span class="mi">2</span><span class="p">]}</span>
<span class="c1">#=> {1=>1, 2=>4, 3=>9, 4=>16, 5=>25}</span>
</code></pre>
<p>Ideally, I request this to be done internally to Ruby without creating an intermediate parent array.</p> Ruby master - Feature #14559 (Closed): ENV.slicehttps://bugs.ruby-lang.org/issues/145592018-02-28T08:39:22Zsawa (Tsuyoshi Sawada)
<p>I would like to request <code>ENV.slice</code>, which should behave analogous to <code>Hash#slice</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">ENV</span><span class="p">.</span><span class="nf">slice</span><span class="p">(</span><span class="s2">"PATH"</span><span class="p">,</span> <span class="s2">"FOO"</span><span class="p">)</span>
<span class="c1"># => {"PATH" => "/foo:/bar", "FOO" => "foo"}</span>
</code></pre> 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 #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 #13314 (Open): dig=https://bugs.ruby-lang.org/issues/133142017-03-14T06:38:37Zsawa (Tsuyoshi Sawada)
<p>We have <code>Hash#dig</code>, and when we want to assign a key-value at a deep level, it is tempting to do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">hash</span><span class="p">.</span><span class="nf">dig</span><span class="p">(</span><span class="ss">:key1</span><span class="p">,</span> <span class="ss">:key2</span><span class="p">,</span> <span class="ss">:key3</span><span class="p">,</span> <span class="ss">:key4</span><span class="p">)</span> <span class="o">=</span> <span class="s2">"value
</span></code></pre>
<p>when we actually needed to do:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">hash</span><span class="p">.</span><span class="nf">dig</span><span class="p">(</span><span class="ss">:key1</span><span class="p">,</span> <span class="ss">:key2</span><span class="p">,</span> <span class="ss">:key3</span><span class="p">)</span><span class="o">&</span><span class="p">.</span><span class="nf">[</span><span class="p">]</span><span class="o">=</span><span class="p">(</span><span class="ss">:key4</span><span class="p">,</span> <span class="s2">"value"</span><span class="p">)</span>
</code></pre>
<p>I propose a method <code>Hash#dig=</code>, which should be equivalent to the following:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Hash</span>
<span class="k">def</span> <span class="nf">dig</span><span class="o">=</span><span class="p">(</span><span class="o">*</span><span class="n">keys</span><span class="p">,</span> <span class="n">final_key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>
<span class="n">dig</span><span class="p">(</span><span class="o">*</span><span class="n">keys</span><span class="p">)</span><span class="o">&</span><span class="p">.</span><span class="nf">[</span><span class="p">](</span><span class="n">final_key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre> Ruby master - Feature #13259 (Open): Kernel#Datehttps://bugs.ruby-lang.org/issues/132592017-02-28T02:17:56Zsawa (Tsuyoshi Sawada)
<p>I often see a piece of code like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="nb">require</span> <span class="s2">"date"</span>
<span class="k">begin</span>
<span class="no">Date</span><span class="p">.</span><span class="nf">strptime</span><span class="p">(</span><span class="n">some_string</span><span class="p">,</span> <span class="n">some_format</span><span class="p">)</span>
<span class="k">rescue</span>
<span class="kp">nil</span>
<span class="k">end</span>
</code></pre>
<p>Since we now have (<a href="https://bugs.ruby-lang.org/issues/12732" class="external">https://bugs.ruby-lang.org/issues/12732</a>) <code>Kernel#Integer</code> with a parameter to avoid raising an error in case of an invalid string, I think that having a counterpart of it in <code>Date</code> would be convenient. I propose <code>Kernel#Date</code>, which works like <code>Date.strptime</code> except that it takes an optional keyword argument, and works as follows:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Date</span><span class="p">(</span><span class="s2">"2017/02/02"</span><span class="p">,</span> <span class="s2">"%Y/%m/%d"</span><span class="p">,</span> <span class="ss">exception: </span><span class="kp">nil</span><span class="p">)</span> <span class="c1"># => #<Date: 2017-02-02 ((2457787j,0s,0n),+0s,2299161j)></span>
<span class="no">Date</span><span class="p">(</span><span class="s2">"foo"</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 #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 #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 #12380 (Open): `Struct` as a subclass of `Class`https://bugs.ruby-lang.org/issues/123802016-05-14T06:22:27Zsawa (Tsuyoshi Sawada)
<p>This issue is somewhat of the same flavor as <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: SingletonClass (Closed)" href="https://bugs.ruby-lang.org/issues/12374">#12374</a>.</p>
<p><code>Struct</code> has a constructor that creates a class:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Struct</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="ss">:foo</span><span class="p">)</span>
<span class="c1"># => #<Class:0x007f605f892cb0></span>
</code></pre>
<p>and this is the same situation with <code>Class</code>.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Class</span><span class="p">.</span><span class="nf">new</span>
<span class="c1"># => #<Class:0x007f605f70c788></span>
</code></pre>
<p>Hence, most naturally, <code>Struct</code> should be a subclass of <code>Class</code>. But in reality, it isn't:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">Struct</span><span class="p">.</span><span class="nf">ancestors</span>
<span class="c1"># => [Struct, Enumerable, Object, Kernel, BasicObject]</span>
</code></pre>
<p>The current structure around <code>Struct</code> is counter-intuitive to me.</p>
<p>I propose that either <code>Struct</code> should be redefined as a subclass of <code>Class</code>, or a new class <code>StructClass</code> should be introduced as a subclass of <code>Class</code>, and take over the functionality of <code>Struct</code>.</p> Ruby master - Feature #12374 (Closed): SingletonClasshttps://bugs.ruby-lang.org/issues/123742016-05-12T18:28:21Zsawa (Tsuyoshi Sawada)
<p>I propose to have a class <code>SingletonClass</code>, a subclass of the class <code>Class</code>, to which all singleton classes belong. It should be the owner of all the properties that are specific to singleton classes. Also, the methods defined on <code>Singleton</code> module should be moved to this class.</p>
<p>Reasons are as follows:</p>
<ol>
<li>
<p>I was thinking that the reason <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: `Class#instance` (Closed)" href="https://bugs.ruby-lang.org/issues/12084">#12084</a> hasn't been seen positively may be because the developers do not want to define a method only on limited instances of a class. If we have <code>SingletonClass</code>, the method <code>#instance</code> proposed in <a class="issue tracker-2 status-5 priority-4 priority-default closed" title="Feature: `Class#instance` (Closed)" href="https://bugs.ruby-lang.org/issues/12084">#12084</a> could be defined as an instance method of <code>SingletonClass</code>.</p>
</li>
<li>
<p>The way to introduce the singleton pattern using the <code>Singleton</code> module (<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>):</p>
</li>
</ol>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">A</span>
<span class="kp">include</span> <span class="no">Singleton</span>
<span class="c1"># ...</span>
<span class="k">end</span>
</code></pre>
<p>is a bit unnatural and verbose. If we have <code>SingletonClass</code>, then we can define a singleton class more naturally:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="no">A</span> <span class="o">=</span> <span class="no">SingletonClass</span><span class="p">.</span><span class="nf">new</span>
</code></pre> Ruby master - Feature #12333 (Closed): `String#concat`, `Array#concat`, `String#prepend` to take ...https://bugs.ruby-lang.org/issues/123332016-04-30T12:25:13Zsawa (Tsuyoshi Sawada)
<p>I would like <code>String#concat</code>, <code>Array#concat</code>, <code>String#prepend</code> to take multiple arguments</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">s</span> <span class="o">=</span> <span class="s2">""</span>
<span class="n">s</span><span class="p">.</span><span class="nf">concat</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">prepend</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">s</span> <span class="c1"># => "ABCabc"</span>
<span class="n">a</span> <span class="o">=</span> <span class="p">[]</span>
<span class="n">a</span><span class="p">.</span><span class="nf">concat</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">a</span> <span class="c1"># => ["a", "b", "c"]</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 #12318 (Closed): Returning the evaluated value of a blockhttps://bugs.ruby-lang.org/issues/123182016-04-26T00:53:05Zsawa (Tsuyoshi Sawada)
<p>I often achieve an element using an iterator with a block, and then apply the same/a similar block to the element I get. Examples are:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
<span class="p">.</span><span class="nf">max_by</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span> <span class="o">%</span> <span class="mi">3</span><span class="p">}</span>
<span class="p">.</span><span class="nf">tap</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="k">break</span> <span class="n">e</span> <span class="o">%</span> <span class="mi">3</span><span class="p">}</span>
<span class="c1"># => 2</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="p">.</span><span class="nf">find</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span><span class="p">[</span><span class="sr">/(.)\1/</span><span class="p">]}</span>
<span class="p">.</span><span class="nf">tap</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="k">break</span> <span class="n">e</span><span class="p">[</span><span class="sr">/(.)\1/</span><span class="p">]}</span>
<span class="c1"># => "oo"</span>
</code></pre>
<p>I would like a method on <code>Enumerator</code> that returns the result of the block rather than the original element in the iterator. Not sure about the name, but if I call it <code>and_return</code> temporary, it should look like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
<span class="p">.</span><span class="nf">max_by</span><span class="p">.</span><span class="nf">and_return</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span> <span class="o">%</span> <span class="mi">3</span><span class="p">}</span>
<span class="c1"># => 2</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="p">.</span><span class="nf">find</span><span class="p">.</span><span class="nf">and_return</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span><span class="p">[</span><span class="sr">/(.)\1/</span><span class="p">]}</span>
<span class="c1"># => "oo"</span>
</code></pre> Ruby master - Feature #12317 (Open): Name space of a modulehttps://bugs.ruby-lang.org/issues/123172016-04-26T00:15:58Zsawa (Tsuyoshi Sawada)
<p>I want a method to return the name space of a module, something like:</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">module</span> <span class="nn">B</span><span class="p">;</span> <span class="k">module</span> <span class="nn">C</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">namespace</span> <span class="o">=></span> <span class="p">[</span><span class="no">A</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="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>
</code></pre>
<p>There is <code>nesting</code> method that is similar, but that only returns the lexical nesting information.</p>
<p>There are also some known hacks for this, converting the module to the string representation using <code>to_s</code> or <code>name</code>, and then splitting it by <code>::</code>. But that easily breaks if the module is anonymous, or is a singleton module. I would like a more robust, core method.</p> Ruby master - Feature #12272 (Open): Accepting HTML entity name in string literalhttps://bugs.ruby-lang.org/issues/122722016-04-12T13:00:03Zsawa (Tsuyoshi Sawada)
<p>String literal allows the escape character <code>\u</code> to describe a character using UTF-8 character code like this:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"</span><span class="se">\u</span><span class="s2">201c"</span> <span class="c1"># left double quote</span>
<span class="s2">"</span><span class="se">\u</span><span class="s2">2191"</span> <span class="c1"># up arrow</span>
</code></pre>
<p>This is useful in typing characters that are not easy to input from the keyboard. However, normal people do not memorize the UTF-8 codes by heart.</p>
<p>The HTML symbol entity name is the place where we can compromise (although it is not available for the entire UTF-8), I think. I would like the string literal to be extended to accept HTML entity names and interpret them as the corresponding UTF-8 characters. I do not have a definite idea for the syntax, but a candidate can be an escape character <code>\& ... ;</code>, so that we can type:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"</span><span class="se">\&</span><span class="s2">ldquo;"</span> <span class="c1"># left double quote</span>
<span class="s2">"</span><span class="se">\&</span><span class="s2">uarr;"</span> <span class="c1"># up arrow</span>
</code></pre>
<p>Currently, <code>"\&"</code> is interpreted as <code>"&"</code>, so this will be a compatibility breaking change, and if that is not desirable, perhaps a different syntax may be considered.</p> Ruby master - Feature #12262 (Open): Anti-loophttps://bugs.ruby-lang.org/issues/122622016-04-08T07:21:19Zsawa (Tsuyoshi Sawada)
<p>The <code>loop</code> method continues by default, and requires the keyword <code>break</code> to escape. This is good when the continuing cases are the norm and the escaping cases are exceptional:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="kp">loop</span> <span class="k">do</span>
<span class="o">...</span>
<span class="k">if</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">break</span> <span class="c1"># breaks on exceptional cases</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">else</span>
<span class="o">...</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>But when the continuing cases are exceptional and the escaping cases are the norm, the construction requires a lot of <code>break</code>, and it becomes cumbersome:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="kp">loop</span> <span class="k">do</span>
<span class="o">...</span>
<span class="k">if</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">break</span> <span class="c1"># lot of breaks</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">break</span> <span class="c1"># lot of breaks</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">break</span> <span class="c1"># lot of breaks</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">else</span>
<span class="o">...</span>
<span class="k">break</span> <span class="c1"># lot of breaks</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>I actually see this use case a lot when user input is asked with validation on a command line script.</p>
<p>I request a <code>loop</code>-like method that works in the opposite way to <code>loop</code>, that is, it escapes (i.e., runs only once) by default, and requires a keyword to continue (perhaps <code>next</code>). The second code above would then be written like:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">some_loop_like_method</span> <span class="k">do</span>
<span class="o">...</span>
<span class="k">if</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">elsif</span> <span class="o">...</span>
<span class="o">...</span>
<span class="k">next</span> <span class="c1"># continues on exceptional cases</span>
<span class="k">else</span>
<span class="o">...</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre> Ruby master - Feature #12173 (Open): `Time#till_now`https://bugs.ruby-lang.org/issues/121732016-03-14T16:57:25Zsawa (Tsuyoshi Sawada)
<p>It is very frequent to have a time instance:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">t</span> <span class="o">=</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span>
</code></pre>
<p>and then after some operations, do:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="no">Time</span><span class="p">.</span><span class="nf">now</span> <span class="o">-</span> <span class="n">t</span>
</code></pre>
<p>I propose <code>Time#till_now</code>, which is equivalent to:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="k">class</span> <span class="nc">Time</span>
<span class="k">def</span> <span class="nf">till_now</span><span class="p">;</span> <span class="nb">self</span><span class="p">.</span><span class="nf">class</span><span class="p">.</span><span class="nf">now</span> <span class="o">-</span> <span class="nb">self</span> <span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>and similar methods can perhaps be defined on <code>Date</code> and <code>DateTime</code> classes as well. Another candidate for the method name is <code>until_now</code>.</p>
<p>Then we can do:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">t</span> <span class="o">=</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span>
<span class="c1"># some heavy operation</span>
<span class="nb">puts</span> <span class="s2">"It took </span><span class="si">#{</span><span class="n">t</span><span class="p">.</span><span class="nf">till_now</span><span class="si">}</span><span class="s2"> secs."</span>
</code></pre> 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 #12134 (Open): Comparison between `true` and `false`https://bugs.ruby-lang.org/issues/121342016-03-02T10:56:01Zsawa (Tsuyoshi Sawada)
<p>There are some needs to sort elements depending on whether they satisfy certain condition expressed as a predicate. For example, to place prime numbers before others:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="nb">require</span> <span class="s2">"prime"</span>
<span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">4</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">1</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="no">Prime</span><span class="p">.</span><span class="nf">prime?</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="p">?</span> <span class="mi">0</span> <span class="p">:</span> <span class="mi">1</span><span class="p">}</span> <span class="c1"># => [7, 5, 3, 2, 6, 4, 1]</span>
</code></pre>
<p>or to do such sort with the secondary condition to sort by the size:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">4</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">1</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="no">Prime</span><span class="p">.</span><span class="nf">prime?</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="p">?</span> <span class="mi">0</span> <span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [2, 3, 5, 7, 1, 4, 6]</span>
</code></pre>
<p>Here, the temporal assignment of magic numbers <code>0</code> and <code>1</code> is ad hoc, but ordering between <code>true</code> and <code>false</code> makes sense. And given that there are <code>if</code> construction (which is unmarked case compared to the <code>unless</code> construction) and the ternary operator, in which the truthy branch is placed before the falsy branch, I think it makes sense to assume an inherent ordering of <code>true</code> being placed before <code>false</code>.</p>
<p>So I propose comparison between <code>true</code> and <code>false</code>:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="kp">true</span> <span class="o"><=></span> <span class="kp">false</span> <span class="c1"># => -1</span>
<span class="kp">false</span> <span class="o"><=></span> <span class="kp">true</span> <span class="c1"># => 1</span>
</code></pre>
<p>Using this, the cases above can be written more directly as:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">4</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">1</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="no">Prime</span><span class="p">.</span><span class="nf">prime?</span><span class="p">(</span><span class="n">e</span><span class="p">)}</span> <span class="c1"># => [7, 5, 3, 2, 6, 4, 1]</span>
<span class="p">[</span><span class="mi">7</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">4</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">1</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="no">Prime</span><span class="p">.</span><span class="nf">prime?</span><span class="p">(</span><span class="n">e</span><span class="p">),</span> <span class="n">e</span><span class="p">]}</span> <span class="c1"># => [2, 3, 5, 7, 1, 4, 6]</span>
</code></pre>
<hr>
<p>Please do not confuse this with the common proposal to map booleans to integers, particularly <code>true.to_i # => 1</code> and <code>false.to_i # => 0</code>. That is arbitrary, and does not make sense. In fact, my proposal goes against such proposal (under the proposal to map booleans, <code>true.to_i <=> false.to_i</code> translates to <code>1 <=> 0 # => 1</code>, which goes against my proposal <code>true <=> false # => 01</code>).</p> Ruby master - Feature #12116 (Open): `Fixnum#divmod`, `Bignum#divmod` with multiple argumentshttps://bugs.ruby-lang.org/issues/121162016-02-26T18:04:45Zsawa (Tsuyoshi Sawada)
<p>Sometimes, I need to apply <code>divmod</code> repeatedly. For example, in order to convert a number expressing seconds into approx year, day, hour, minutes, seconds (approx in the sense of ignoring leap day and leap second), I can repeatedly apply <code>divmod</code>:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">seconds</span> <span class="o">=</span> <span class="mi">289342751</span>
<span class="n">minutes</span><span class="p">,</span> <span class="n">seconds</span> <span class="o">=</span> <span class="n">seconds</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">60</span><span class="p">)</span> <span class="c1"># => [4822379, 11]</span>
<span class="n">hours</span><span class="p">,</span> <span class="n">minutes</span> <span class="o">=</span> <span class="n">minutes</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">60</span><span class="p">)</span> <span class="c1"># => [80372, 59]</span>
<span class="n">days</span><span class="p">,</span> <span class="n">hours</span> <span class="o">=</span> <span class="n">hours</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">24</span><span class="p">)</span> <span class="c1"># => [3348, 20]</span>
<span class="n">years</span><span class="p">,</span> <span class="n">days</span> <span class="o">=</span> <span class="n">days</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">365</span><span class="p">)</span> <span class="c1"># => [9, 63]</span>
</code></pre>
<p>so that I get that 289342751 seconds is approx 9 years 63 days 20 hours 59 minutes and 11 seconds. But it is cumbersome to do all that. It would be convenient if <code>divmod</code> can take multiple arguments so that the conventional <code>divmod</code> is applied from the right-most argument to the left, returning the above result at once:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="mi">289342751</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">365</span><span class="p">,</span> <span class="mi">24</span><span class="p">,</span> <span class="mi">60</span><span class="p">,</span> <span class="mi">60</span><span class="p">)</span> <span class="c1"># => [9, 63, 20, 59, 11]</span>
</code></pre>
<p>In general, when <code>n</code> arguments are passed to the proposed <code>divmod</code>, an array of <code>n + 1</code> elements should be returned.</p>
<p>Another use case is nested arrays. Some people tend to express a matrix as a nested array, and try to access the innermost elements using multiple indices. To list the coordinates of the occurrences of <code>1</code>, one may do:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">m</span> <span class="o">=</span> <span class="p">[</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">0</span><span class="p">],</span>
<span class="p">[</span><span class="mi">0</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="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">],</span>
<span class="p">]</span>
<span class="n">a</span> <span class="o">=</span> <span class="p">[]</span>
<span class="n">m</span><span class="p">.</span><span class="nf">each_with_index</span> <span class="k">do</span> <span class="o">|</span><span class="n">row</span><span class="p">,</span> <span class="n">i</span><span class="o">|</span>
<span class="n">row</span><span class="p">.</span><span class="nf">each_with_index</span> <span class="k">do</span> <span class="o">|</span><span class="n">e</span><span class="p">,</span> <span class="n">j</span><span class="o">|</span>
<span class="n">a</span><span class="p">.</span><span class="nf">push</span><span class="p">([</span><span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">])</span> <span class="k">if</span> <span class="n">e</span> <span class="o">==</span> <span class="mi">1</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="n">a</span> <span class="c1"># => [[0, 0], [1, 1], [2, 2]]</span>
</code></pre>
<p>But it is often easier to have a flat array and use <code>divmod</code> with it:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">m</span> <span class="o">=</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">0</span><span class="p">,</span>
<span class="mi">0</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">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span>
<span class="p">]</span>
<span class="n">m</span><span class="p">.</span><span class="nf">each</span><span class="p">.</span><span class="nf">with_index</span><span class="p">.</span><span class="nf">select</span><span class="p">{</span><span class="o">|</span><span class="n">e</span><span class="p">,</span> <span class="n">_</span><span class="o">|</span> <span class="n">e</span> <span class="o">==</span> <span class="mi">1</span><span class="p">}.</span><span class="nf">map</span><span class="p">{</span><span class="o">|</span><span class="n">_</span><span class="p">,</span> <span class="n">i</span><span class="o">|</span> <span class="n">i</span><span class="p">.</span><span class="nf">divmod</span><span class="p">(</span><span class="mi">3</span><span class="p">)}</span> <span class="c1"># => [[0, 0], [1, 1], [2, 2]]</span>
</code></pre>
<p>However, once the nesting achieves another level, it becomes cumbersome. Instead of using a nested array:</p>
<pre><code class="RUBY syntaxhl" data-language="RUBY"><span class="n">t</span> <span class="o">=</span> <span class="p">[</span>
<span class="p">[</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="s2">"d"</span><span class="p">],</span>
<span class="p">],</span>
<span class="p">[</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="s2">"d"</span><span class="p">],</span>
<span class="p">],</span>
<span class="p">]</span>
</code></pre>
<p>one can keep using a flat array, but that would require repeated application of <code>divmod</code> to covert between the flat index and the nested index. The proposed feature would also help in such case.</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 - 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 #12059 (Open): `Array#single?`, `Hash#single?`https://bugs.ruby-lang.org/issues/120592016-02-09T15:37:03Zsawa (Tsuyoshi Sawada)
<p>There are some use cases when one wants to check if an array or a hash has exactly one element. I propose <code>Array#single?</code> and <code>Hash#single?</code> that checks for such cases and returns either <code>true</code> or <code>false</code>. This is an analogy from the <code>empty?</code> method on the respective class.</p>
<ul>
<li>When creating an inflectional form out of an array:</li>
</ul>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"object1"</span><span class="p">,</span> <span class="s2">"object2"</span><span class="p">]</span>
<span class="s2">"There </span><span class="si">#{</span><span class="n">a</span><span class="p">.</span><span class="nf">single</span> <span class="p">?</span> <span class="s2">"is"</span> <span class="p">:</span> <span class="s2">"are"</span><span class="si">}</span><span class="s2"> </span><span class="si">#{</span><span class="n">a</span><span class="p">.</span><span class="nf">length</span><span class="si">}</span><span class="s2"> </span><span class="si">#{</span><span class="n">a</span><span class="p">.</span><span class="nf">single?</span> <span class="p">?</span> <span class="s2">"object"</span> <span class="p">:</span> <span class="s2">"objects"</span><span class="si">}</span><span class="s2">."</span>
<span class="c1"># => "There are 2 objects."</span>
</code></pre>
<ul>
<li>When checking if all elements of the array are the same:</li>
</ul>
<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">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">].</span><span class="nf">uniq</span><span class="p">.</span><span class="nf">single?</span> <span class="c1"># => false</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">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">].</span><span class="nf">uniq</span><span class="p">.</span><span class="nf">single?</span> <span class="c1"># => true</span>
</code></pre> Ruby master - Feature #11951 (Closed): `RubyVM::InstructionSequence.compile` should return the er...https://bugs.ruby-lang.org/issues/119512016-01-05T07:35:55Zsawa (Tsuyoshi Sawada)
<p>When <code>RubyVM::InstructionSequence.compile</code> raises a syntax error, it outputs the syntax error message to <code>$stderr</code>, and then raises a <code>SyntaxError</code> anyway, whose message is simply: <code>"compile error"</code>.</p>
<p>I don't think this is useful. For example, if I want to analyze within Ruby code whether a certain string is syntactically correct Ruby code, I would have to reasign <code>$stderr</code> to something such as <code>StringIO.new</code>, run <code>RubyVM::InstructionSequence.compile</code>, rescue the syntax error, (but instead of reading the error message from the error), read the error message by doing <code>$stderr.string</code>. This is cumbersome.</p>
<p>On the other hand, there is <code>eval</code>, which also can raise a SyntaxError. But with <code>eval</code>, the error message comes out with the raised error, and is useful. I don't see any reason why <code>RubyVM::InstructionSequence.compile</code> should behave differently from <code>eval</code> with respect to returning the error message.</p>
<p>I request <code>RubyVM::InstructionSequence.compile</code> to return the error message as the message on the raised error rather than directly printing it to <code>$stderr</code>.</p> Ruby master - Feature #11939 (Open): Syntax sugar to apply a method replace a variablehttps://bugs.ruby-lang.org/issues/119392016-01-02T13:59:28Zsawa (Tsuyoshi Sawada)
<p>There is frequent use case to modify the value of a variable and keep it referred to by the same variable name. When method chaining cannot be done (for example, when the method is conditionally called), the same variable name would have to be repeated:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="n">var</span> <span class="o">=</span> <span class="n">var</span><span class="p">.</span><span class="nf">some_method</span><span class="p">(</span><span class="n">some_args</span><span class="p">)</span> <span class="k">if</span> <span class="n">some_condition</span>
<span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="o">...</span>
</code></pre>
<p>I would like to propose a syntax sugar for this kind of situation. I have two options in mind.</p>
<p>(1) <code>=.</code></p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="n">var</span> <span class="o">=</span><span class="p">.</span><span class="nf">some_method</span><span class="p">(</span><span class="n">some_args</span><span class="p">)</span> <span class="k">if</span> <span class="n">some_condition</span>
<span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="o">...</span>
</code></pre>
<p>(2) <code>.=</code></p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="n">var</span> <span class="p">.</span><span class="nf">=</span> <span class="n">some_method</span><span class="p">(</span><span class="n">some_args</span><span class="p">)</span> <span class="k">if</span> <span class="n">some_condition</span>
<span class="n">var</span> <span class="o">=</span> <span class="o">...</span>
<span class="o">...</span>
</code></pre>
<p>Notation (2) seems to be in line with syntax sugar like <code>+=</code>, but option (1) has the advantage that the period comes together with the method name.</p> 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 #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 - Feature #11818 (Closed): `Hash#compact`https://bugs.ruby-lang.org/issues/118182015-12-15T05:09:54Zsawa (Tsuyoshi Sawada)
<p>I request <code>Hash#compact</code> and <code>Hash#compact!</code> that remove the key-value pairs whose value is <code>nil</code>, as follows:</p>
<pre><code>h1 = {a:, 1, b: nil, c: 2}
h1.compact # => {a: 1, c: 2}
h1 # => {a: 1, b: nil, c: 2}
h2 = {a:, 1, b: nil, c: 2}
h2.compact! # => {a: 1, c: 2}
h2 # => {a: 1, c: 2}
h3 = {a:, 1, c: 2}
h3.compact! # => nil
h3 # => {a: 1, c: 2}
</code></pre>
<p>I believe people have frequent need to do this.</p> 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 #11568 (Closed): Misleading warning for duplicate keys in a hashhttps://bugs.ruby-lang.org/issues/115682015-10-05T20:41:10Zsawa (Tsuyoshi Sawada)
<p>When a hash literal has duplicate keys as follows,</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">{</span>
<span class="ss">a: </span><span class="s2">"foo"</span><span class="p">,</span>
<span class="ss">a: </span><span class="s2">"bar"</span><span class="p">,</span>
<span class="p">}</span>
</code></pre>
<p>the warning message goes as follows:</p>
<pre><code>warning: duplicated key at line 3 ignored: :a
</code></pre>
<p>This message gives the impression as if it is the value <code>"bar"</code> at line 3 that is ignored, even though in reality it is the value <code>"foo"</code> at line 2 that is ignored. It is misleading. I suggest the message to be changed.</p> Ruby master - Feature #11309 (Open): Iterator over string matcheshttps://bugs.ruby-lang.org/issues/113092015-06-26T14:55:43Zsawa (Tsuyoshi Sawada)
<p>This was hinted from a problem in stackoverflow (<a href="http://stackoverflow.com/questions/31074050/build-list-of-strings-containing-substrings-separated-by-an-from-a-string/31075511#31075511" class="external">http://stackoverflow.com/questions/31074050/build-list-of-strings-containing-substrings-separated-by-an-from-a-string/31075511#31075511</a>).</p>
<p>Suppose there is a string:</p>
<pre><code>s = "a_b_c_d_e"
</code></pre>
<p>To get an array of pre-matches that result from matching <code>s</code> with <code>"_"</code>, I can do this:</p>
<pre><code>a = []
s.scan("_"){a.push($`)}
a # => ["a", "a_b", "a_b_c", "a_b_c_d"]
</code></pre>
<p>But this looks too Perlish. I thought it would be nice if there is a method on <code>String</code> that creates an enumerator over matches so that I can do something like this:</p>
<pre><code>"a_b_c_d_e".some_method("_").with_object([]){|m, a| a.push(m.post_match)}
# => ["a", "a_b", "a_b_c", "a_b_c_d"]
</code></pre>
<p>where <code>m</code> is the last matchdata instance at that point. I believe such method would have wider application.</p> 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 #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 #10769 (Closed): Negative counterpart to Enumerable#slice_whenhttps://bugs.ruby-lang.org/issues/107692015-01-22T00:35:57Zsawa (Tsuyoshi Sawada)
<p>It seems to me that most useful cases of <code>Enumerable#slice_when</code> involve a negative condition inside the block. That observation seems to be confirmed by the official examples in <a href="http://docs.ruby-lang.org/ja/2.2.0/method/Enumerable/i/slice_when.html" class="external">http://docs.ruby-lang.org/ja/2.2.0/method/Enumerable/i/slice_when.html</a>. In these examples, the conditions inside the block are negations of what would is intended (which is expressed in the comment above each code).</p>
<pre><code># 1ずつ増加する部分配列ごとに分ける。
[1,2,4,9,10,11,12,15,16,19,20,21]
.slice_when{|i, j| i + 1 != j}.to_a # => [[1, 2], [4], [9, 10, 11, 12], [15, 16], [19, 20, 21]]
# ソート済の配列を近い値(差が6以内)の部分配列ごとに分ける。
[3, 11, 14, 25, 28, 29, 29, 41, 55, 57]
.slice_when{|i, j| 6 < j - i}.to_a # => [[3], [11, 14], [25, 28, 29, 29], [41], [55, 57]]
# 増加のみの部分配列ごとに分ける。
[0, 9, 2, 2, 3, 2, 7, 5, 9, 5]
.slice_when{|i, j| i > j}.to_a # => [[0, 9], [2, 2, 3], [2, 7], [5, 9], [5]]
# 隣り合う偶数同士、奇数同士の部分配列ごとに分ける。
[7, 5, 9, 2, 0, 7, 9, 4, 2, 0]
.slice_when{|i, j| i.even? != j.even?}.to_a # => [[7, 5, 9], [2, 0], [7, 9], [4, 2, 0]]
</code></pre>
<p>I propose that there should be a method on <code>Enumerable</code> that works like <code>slice_when</code> except that it works with the block negatively as compared to <code>slice_when</code>. Let us call this method <code>Enumerable#chunk_while</code>. Then, the examples above would be written more naturally without having a negative notion in the blocks.</p>
<pre><code># 1ずつ増加する部分配列ごとに分ける。
[1,2,4,9,10,11,12,15,16,19,20,21]
.chunk_while{|i, j| i + 1 == j}.to_a
# ソート済の配列を近い値(差が6以内)の部分配列ごとに分ける。
[3, 11, 14, 25, 28, 29, 29, 41, 55, 57]
.chunk_while{|i, j| j - i <= 6}.to_a
# 増加のみの部分配列ごとに分ける。
[0, 9, 2, 2, 3, 2, 7, 5, 9, 5]
.chunk_while{|i, j| i <= j}.to_a
# 隣り合う偶数同士、奇数同士の部分配列ごとに分ける。
[7, 5, 9, 2, 0, 7, 9, 4, 2, 0]
.chunk_while{|i, j| i.even? == j.even?}.to_a
</code></pre>
<p>I am not sure about the method name. There can be a better name.</p> Ruby master - Feature #10729 (Open): Array method to subtract in placehttps://bugs.ruby-lang.org/issues/107292015-01-10T22:36:02Zsawa (Tsuyoshi Sawada)
<p>I request a method on array that takes another array, subtract that from self in place (= destructively), and return the subtracted elements:</p>
<pre><code>a = [1, 2, 3, 4, 5]
a.some_method([2, 4, 6]) #=> [2, 4]
a #=> [1, 3, 5]
</code></pre>
<p>Ideally, it should also allow a block:</p>
<pre><code>a = [1, 2, 3, 4, 5]
a.some_method(&:even?) #=> [2, 4]
a #=> [1, 3, 5]
</code></pre>
<p>This operation is quite frequent, but at the moment, it requires several steps to do.</p> Ruby master - Feature #10426 (Open): A predicate to express congruencehttps://bugs.ruby-lang.org/issues/104262014-10-26T00:55:20Zsawa (Tsuyoshi Sawada)
<p>I occasionally felt the necessity of a predicate that checks congruence with respect to some operations:</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">equal_by?</span> <span class="n">other</span><span class="p">,</span> <span class="o">&</span><span class="n">pr</span>
<span class="n">pr</span><span class="p">.</span><span class="nf">call</span><span class="p">(</span><span class="nb">self</span><span class="p">)</span> <span class="o">==</span> <span class="n">pr</span><span class="p">.</span><span class="nf">call</span><span class="p">(</span><span class="n">other</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">alias</span> <span class="n">congruent?</span> <span class="n">equal_by?</span>
<span class="k">end</span>
<span class="mi">5</span><span class="p">.</span><span class="nf">congruent?</span><span class="p">(</span><span class="mi">2</span><span class="p">){</span><span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span> <span class="o">%</span> <span class="mi">3</span><span class="p">}</span> <span class="c1">#=> true</span>
<span class="s2">"HELLO"</span><span class="p">.</span><span class="nf">equal_by?</span><span class="p">(</span><span class="s2">"Hello"</span><span class="p">,</span> <span class="o">&</span><span class="ss">:downcase</span><span class="p">)</span> <span class="c1">#=> true</span>
</code></pre> Ruby master - Feature #10425 (Open): A predicate method to tell if a number is near anotherhttps://bugs.ruby-lang.org/issues/104252014-10-26T00:38:58Zsawa (Tsuyoshi Sawada)
<p>A method <code>near?</code> like the following would be useful.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">class</span> <span class="nc">Numeric</span>
<span class="k">def</span> <span class="nf">near?</span> <span class="n">other</span><span class="p">,</span> <span class="ss">delta: </span><span class="no">Float</span><span class="o">::</span><span class="no">EPSILON</span>
<span class="p">(</span><span class="n">other</span><span class="p">.</span><span class="nf">to_f</span> <span class="o">-</span> <span class="n">to_f</span><span class="p">).</span><span class="nf">abs</span> <span class="o"><=</span> <span class="n">delta</span><span class="p">.</span><span class="nf">to_f</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">class</span> <span class="nc">Time</span>
<span class="k">def</span> <span class="nf">near?</span> <span class="n">other</span><span class="p">,</span> <span class="ss">delta: </span><span class="no">Float</span><span class="o">::</span><span class="no">EPSILON</span>
<span class="n">to_f</span><span class="p">.</span><span class="nf">near?</span><span class="p">(</span><span class="n">other</span><span class="p">.</span><span class="nf">to_f</span><span class="p">,</span> <span class="ss">delta: </span><span class="n">delta</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
<p>It can be used to check errors, or whether something is around something.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mf">23.24324</span><span class="p">.</span><span class="nf">near?</span><span class="p">(</span><span class="mf">23.23</span><span class="p">,</span> <span class="ss">delta: </span><span class="mf">0.5</span><span class="p">)</span> <span class="c1"># => true</span>
<span class="n">t1</span> <span class="o">=</span> <span class="n">t2</span> <span class="o">=</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span>
<span class="n">t3</span> <span class="o">=</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span>
<span class="n">t1</span><span class="p">.</span><span class="nf">near?</span><span class="p">(</span><span class="n">t2</span><span class="p">)</span> <span class="c1">#=> true</span>
<span class="n">t1</span><span class="p">.</span><span class="nf">near?</span><span class="p">(</span><span class="n">t3</span><span class="p">)</span> <span class="c1">#=> false</span>
<span class="mi">5</span><span class="p">.</span><span class="nf">near?</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="ss">delta: </span><span class="mi">1</span><span class="p">)</span> <span class="c1">#=> true</span>
</code></pre>
<p>Some testing frameworks have something similar to this, but I think this is an elementary concept that Ruby should support at it core.</p> Ruby master - Feature #10366 (Open): New inspection form for rationalhttps://bugs.ruby-lang.org/issues/103662014-10-11T00:50:15Zsawa (Tsuyoshi Sawada)
<p>Currently, rational inspection is expressed with parentheses:</p>
<pre><code>(2/51)
</code></pre>
<p>If this were taken as a Ruby expression, it would mean integer division, whose value is <code>0</code> in this case. It does not make much sense to express that it is indeed not integer division and that it is rational by using parentheses. Now that we have rational literal using <code>r</code>, we can make the inspection form as:</p>
<pre><code>2/51r
</code></pre>
<p>This would be much less confusing.</p> Ruby master - Feature #10332 (Open): Rational literal for mixed fractionshttps://bugs.ruby-lang.org/issues/103322014-10-06T14:55:48Zsawa (Tsuyoshi Sawada)
<p>Current behavior of rational literal and <code>String#to_r</code> does not recognize mixed fractions. Mixed fraction is not rare, and is frequently used in places such as US length measurement.</p>
<p><img src="http://www.strongtie.com/graphics/anchorsystems/catalog/tables/217b-2012.gif" alt="drill bits"></p>
<p>I propose that rational literal and <code>String#to_r</code> should be extended to handle mixed fractions. Perhaps something like:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="mi">8</span> <span class="mi">1</span><span class="o">/</span><span class="mi">2</span><span class="n">r</span> <span class="c1">#=> (17/2)</span>
<span class="s2">"8 1/2"</span><span class="p">.</span><span class="nf">to_r</span> <span class="c1">#=> (17/2)</span>
</code></pre>
<p>or</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="p">(</span><span class="mi">8</span> <span class="mi">1</span><span class="o">/</span><span class="mi">2</span><span class="p">)</span><span class="n">r</span> <span class="c1">#=> (17/2)</span>
</code></pre> Ruby master - Feature #10331 (Open): String#to_r to recognize negative denominatorshttps://bugs.ruby-lang.org/issues/103312014-10-06T14:44:18Zsawa (Tsuyoshi Sawada)
<p>Current behavior or <code>String#to_r</code> does not recognize negative denominators. This can lead to confusing results:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"1/-3"</span><span class="p">.</span><span class="nf">to_r</span>
<span class="c1">#=> (1/1)</span>
</code></pre>
<p>I propose negative denominators to be recognized.</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="s2">"1/-3"</span><span class="p">.</span><span class="nf">to_r</span>
<span class="c1">#=> (-1/3)</span>
</code></pre> Ruby master - Feature #10183 (Open): An alternative name for method `class`https://bugs.ruby-lang.org/issues/101832014-08-29T12:52:13Zsawa (Tsuyoshi Sawada)
<p>The method <code>class</code> is special in that it always has to have an explicit receiver in order to avoid crash with the keyword <code>class</code>. But this is very inconvenient. I have seen so many</p>
<pre><code>self.class
</code></pre>
<p>in codes. I propose that there should be an alternative name for this method so that it can be used with an implicit receiver, and the method name <code>class</code> should be gradually depricated.</p>
<p>As for the name, I have no clear idea. I can only think of <code>klass</code>, but perhaps someone else might come up with a better name.</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 #9805 (Closed): Backtrace for SystemStackErrorhttps://bugs.ruby-lang.org/issues/98052014-05-05T20:11:50Zsawa (Tsuyoshi Sawada)
<p>The following code:</p>
<pre><code>def a; a end
begin
a
rescue => e
puts e.backtrace.inspect
end
</code></pre>
<p>only returns a single line of backtrace like:</p>
<pre><code>/tmp/scratch:3:in `a'
</code></pre>
<p>but this is not helpful when debugging. It would be better if some limit be set by configuration, and the backtrace is displayed as far as possible within the limit, so the case above would become:</p>
<pre><code>/tmp/scratch:3:in `a'
/tmp/scratch:3:in `a'
/tmp/scratch:3:in `a'
... # repeated as many times as the limit set
/tmp/scratch:3:in `a'
</code></pre>
<p>I believe the same question was asked here: <a href="https://bugs.ruby-lang.org/issues/6216" class="external">https://bugs.ruby-lang.org/issues/6216</a>, but the code posted by the poster was unnecessarily long and complex that the intent was not clear to many people.</p> Ruby master - Feature #9768 (Assigned): Method that is visible only within a certain module/classhttps://bugs.ruby-lang.org/issues/97682014-04-22T09:57:35Zsawa (Tsuyoshi Sawada)
<p>Some frameworks/libraries monkeypatch their own methods on Ruby core classes like <code>String</code>, <code>Hash</code>, <code>Array</code>, etc., and that is often causing problems/concerns of name conflict.</p>
<p>Seeing that these custom methods are used only in the context of a certain module/class, I request for a way to define a method (<code>foo</code>) on a module/class (<code>A</code>) so that it will be visible only from within a specified module/class (<code>B</code>) or its descendants. The following illustrates this situation:</p>
<pre><code>A.new.foo # => undefined
class B
A.new.foo # => defined
def bar
A.new.foo # => defined
end
def self.baz
A.new.foo # => defined
end
end
class C < B
A.new.foo # => defined
def bar
A.new.foo # => defined
end
def self.baz
A.new.foo # => defined
end
end
</code></pre>
<p>I do not have a certain syntax for this in mind, but I think it can be made much simpler, compared to the complicated syntax of refinement.</p>
<p>This is reminiscent of refinement, but they are pretty much different.</p>
<p>Refinement's purpose is to let certain methods be accessible from only a certain file. A typical use case would be a library developer defining their methods to be used from within the library and making such methods inaccessible from the end user.</p>
<p>On the other hand, the idea I am proposing here is for making method accessible from any file, but only within a certain module/class. A typical use case would be defining a method to be used by an end user, but only from within a context of certain module/class.</p> Ruby master - Feature #9667 (Open): Optimization of __FILE__ and __dir__https://bugs.ruby-lang.org/issues/96672014-03-24T09:19:04Zsawa (Tsuyoshi Sawada)
<p>In the same spirit as the string literal followed by <code>freeze</code> is optimized, I think <code>__FILE__</code> and <code>__dir__</code> should be optimized. Currently, they return different object id each time they are called.</p>
<pre><code>__FILE__.object_id # => 70183725179420
__FILE__.object_id # => 70183725129020
...
</code></pre>
<p>I propose them to be optimized so that they are only created once per occurrence.</p>
<pre><code>__FILE__.object_id # => 70183725179420
__FILE__.object_id # => 70183725179420
...
</code></pre> 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 #9557 (Open): Enumerator#next and Enumerator#peek with argumenthttps://bugs.ruby-lang.org/issues/95572014-02-23T09:14:18Zsawa (Tsuyoshi Sawada)
<p>It often happens that I want to move the current index of an enumerator by some arbitrary number <code>n</code>. <code>Enumerator#feed</code> takes the element as the argument, but that cannot be used if the enumerator has duplicate elements, or when I do not have information of a particular element to choose but just want to increment the index by some number. <code>Enumerator#next</code>, on the other hand, has a fixed value <code>1</code> to be incremented. It would be convenient if <code>Enumerator#next</code> takes an optional argument that represents the difference of the index to be incremented. The argument can be understood to be defaulted to <code>1</code> when absent.</p>
<p>Also, I often want to look not necessarily the current position, but some position away. It would be good if <code>Enumerator#peek</code> takes an optional argument that represents the positional difference to be peeked. The argument can be understood to be defaulted to <code>0</code> when absent.</p>
<pre><code>enum = [0, 1, 2, 3, 4, 5, 6, 7, 8].to_enum
enum.peek # => 0
enum.peek(0) # => 0
enum.peek(1) # => 1
enum.peek # => 0
enum.next # => 0
enum.next(1) # => 1
enum.next(2) # => 2
enum.peek # => 4
enum.peek(0) # => 4
enum.peek(1) # => 5
enum.peek # => 4
enum.next # => 4
enum.next(1) # => 5
enum.next(2) # => 6
peek # => 8
</code></pre> 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 - Misc #9503 (Rejected): Request for a Question and Answer sectionhttps://bugs.ruby-lang.org/issues/95032014-02-08T20:14:25Zsawa (Tsuyoshi Sawada)
<p>I often come up with a question regarding why Ruby is designed the way it is with respect to a certain specification. Without knowing why it was designed in that way, I usually start to feel that such thing should be in a different way, and I ask that as a feature on this site, but then, sometimes it is responded from the developers with a reason why it has to be the way it is.</p>
<p>When I have such question, I first try to look for answers about the design decision; especially, I am a frequent user of a Question and Answer site called StackOverflow (stackoverflow.com), and whenever I ask that kind of question, it ends up with the consensus being "Ask Matz". Afterall, only Matz (or the core developers) knows.</p>
<p>So, I request a Question and Answer section on this site regarding design decisions about Ruby: Why a certain feature was designed in such way and not in another way. I think this is the right place where such thing should be because only the developers know the reason. Then, people can ask about why a certain design decision was made before posting a feature request, and that will reduce hopeless feature requests that end up being rejected. That would be of a benefit to both the developers and the people wondering about the design.</p> Ruby master - Feature #9111 (Open): Encoding-free String comparisonhttps://bugs.ruby-lang.org/issues/91112013-11-14T22:15:06Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
Currently, strings with the same content but with different encodings count as different strings. This causes strange behaviour as below (noted in StackOverflow question <a href="http://stackoverflow.com/questions/19977788/strange-behavior-in-packed-ruby-strings#19978206" class="external">http://stackoverflow.com/questions/19977788/strange-behavior-in-packed-ruby-strings#19978206</a>):</p>
<pre><code>[128].pack("C") # => "\x80"
[128].pack("C") == "\x80" # => false
</code></pre>
<p>Since <code>[128].pack("C")</code> has the encoding ASCII-8BIT and <code>"\x80"</code> (by default) has the encoding UTF-8, the two strings are not equal.</p>
<p>Also, comparison of strings with different encodings may end up with a messy, unintended result.</p>
<p>I suggest that the comparison <code>String#<=></code> should not be based on the respective encoding of the strings, but all the strings should be internally converted to UTF-8 for the purpose of comparison.</p>
<p>=end</p> Ruby master - Feature #9071 (Closed): Enumerable#slice_afterhttps://bugs.ruby-lang.org/issues/90712013-11-02T01:21:59Zsawa (Tsuyoshi Sawada)
<p>I see in this discussion: <a href="http://ruby.11.x6.nabble.com/ruby-dev-38392-Enumerable-gather-each-td3534746.html" class="external">http://ruby.11.x6.nabble.com/ruby-dev-38392-Enumerable-gather-each-td3534746.html</a> that <code>Enumerable#slice_before</code> was named as such, having in mind the possibility of <code>Enumerable#slice_after</code> being implemented in the future. I feel the former convenient, but believe the latter should be as well, and am wondering why the latter was not implemented at the same time. I request it to be implemented.</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 #8614 (Open): Object#singleton_class with a blockhttps://bugs.ruby-lang.org/issues/86142013-07-10T01:04:42Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
Most of the time when I use <code>Object#singleton_class</code>, I use it with <code>class_eval</code> following it, like follows:</p>
<pre><code>class Foo
singleton_class.class_eval{attr_accessor :bar}
end
</code></pre>
<p>I think it would be convenient if <code>Object#singleton_class</code> can optionally take a block so that the following will mean the same as above.</p>
<pre><code>class Foo
singleton_class{attr_accessor :bar}
end
</code></pre>
<p>=end</p> Backport193 - Backport #8210 (Closed): Multibyte character interfering with end-line character wi...https://bugs.ruby-lang.org/issues/82102013-04-03T15:22:57Zsawa (Tsuyoshi Sawada)
<p>=begin<br>
With this regex:</p>
<pre><code>regex1 = /\z/
</code></pre>
<p>the following strings match as expected:</p>
<pre><code>"hello" =~ regex1 # => 5
"こんにちは" =~ regex1 # => 5
</code></pre>
<p>but with these regexes:</p>
<pre><code>regex2 = /#$/?\z/
regex3 = /\n?\z/
</code></pre>
<p>they show difference:</p>
<pre><code>"hello" =~ regex2 # => 5
"hello" =~ regex3 # => 5
"こんにちは" =~ regex2 # => nil
"こんにちは" =~ regex3 # => nil
</code></pre>
<p>The string encoding is UTF-8, and the OS is Linux (i.e., <code>$/</code> is <code>"\n"</code>). I expect them to behave the same, and believe this is a bug.<br>
=end</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>