[ruby-core:70825] [Ruby trunk - Feature #11529] [Feedback] extensible % literal declarations

Issue #11529 has been updated by Nobuyoshi Nakada.

Description updated
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?

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Feature #11529: extensible % literal declarations
https://bugs.ruby-lang.org/issues/11529#change-54205

* Author: Eike Dierks
* Status: Feedback
* Priority: Normal
* Assignee: 
----------------------------------------
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



































   








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