Feature #11529: extensible % literal declarations

• Status: Feedback
• Assignee: -
• Target version: -

[eike.rb (Eike Dierks)]

The ruby syntax provides for declaring literals by using the % escapes:

• %q(foo) => 'foo'
• %Q(foo) => "foo"
• %w(foo bar) => ['foo', 'bar']
• %i(foo bar) => [:foo, :bar]

It should be possible to define new % escapes.

Use cases:

I currently use:
%q{select foo from bar}
to quote my sql statements.

It would improve readability to spell that:
%sql{select foo from bar}
(with %sql being an alias of %q [see parsing problems below])

But there could be more interesting uses:

%hash[
   a 1
   b 2]

%triples[
    a b c
    1 2 3]

%json/{"foo":"bar", "zip":"zap"}/

%octal_data[012 345 677]

and the extension code would be something like
def %hash(s)
return ...
end

Notes:

• I did expect this to be a problem. But it's not.

• in my faint memory, old ruby versions were rumoured to parse %sqfooq => "foo"
  but this is no longer true: %sqfooq => SyntaxError: (eval):2: unknown type of %string

• the characters used for enclosing should be clearly defined

• we have two classes:

  • paired chars like () [] {} <>
  • quoting chars like ' " / @ _ # $ %

My Suggestion:

• the quoting chars should be deprecated (try this: %Q%%%%)

• the set of paired chars should be extended to include selected pairs from unicode math symbols

  • unicode does not yet define a plane for open-close-brackets
  • see http://stackoverflow.com/questions/13535172/list-of-all-unicodes-open-close-brackets

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Feedback

Eike Dierks wrote:

• in my faint memory, old ruby versions were rumoured to parse %sqfooq => "foo"
  but this is no longer true: %sqfooq => SyntaxError: (eval):2: unknown type of %string

It has never been true, at least since 1.0.

• the quoting chars should be deprecated (try this: %Q%%%%)

What's the rationale?
I don't think it acceptable because of backward compatibility.

And what does the former half mean?

[mame (Yusuke Endoh)]

I like the idea. Though, I guess it will be hard to agree with the definition syntax and precise semantics.

and the extension code would be something like
def %hash(s)
return ...
end

It conflicts with an existing definition syntax of method named %.

• the quoting chars should be deprecated (try this: %Q%%%%)

Try this: %Q%%%%%%
This is one of the cutest parts of Ruby syntax that I love.

p %%%
p %%\%\%%
p %%%%%%%
puts %%:%+%%-\%s%%%%)%

See also: https://github.com/tric/trick2013/blob/master/yoshi-taka/entry.rb

Anyway. This suggestion is a completely different topic than the first idea (extensible %). We should discuss it in another thread, if really needed.

--
Yusuke Endoh [e-mail]