From: "alexeymuranov (Alexey Muranov)" <redmine@...>
Date: 2012-08-04T23:04:13+09:00
Subject: [ruby-core:46988] [ruby-trunk - Feature #5478] import Set into core, add syntax


Issue #5478 has been updated by alexeymuranov (Alexey Muranov).


=begin
I think that unifying (({Hash})) with (({Set})) could also allow to use the ((*splat*)) star operator more intelligently. For example, currently the following does not work:

 h = { 1 => 2, 3 => 4}
 k = { 0 => 0, *h } # => SyntaxError: unexpected tSTAR, expecting '}'

(i would like to see here k = { 0 => 0, 1 => 2, 3 => 4 } ).

Such behavior could be nice for merging several hashes:

 def f(h); ...; end

 h1 = { :a => 1 }; h2 = { :b => 2 }

 f *h1, *h2, :name => 'foo'

Instead of:

 h = h1.merge(h2)
 h[:name] = 'foo'
 f(h)
=end

----------------------------------------
Feature #5478: import Set into core, add syntax
https://bugs.ruby-lang.org/issues/5478#change-28645

Author: rkh (Konstantin Haase)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 3.0


=begin
A set is a central data structure. However, a lot of Ruby developers use arrays for situations where it would be more reasonable to use a set. One reason for that is that it is way easier to use Array then Set at the moment, another one is that developers are simply not aware it exists.

I propose moving Set from the stdlib to core and possibly add a syntax or a method on array for creating Set literals.

First class syntax suggestions:

    <1, 2, 3>  # might be tricky to parse
    #[1, 2, 3] # would collide with comments
    $[1, 2, 3]
    ${1, 2, 3}

Method suggestions:

    ~[1, 2, 3]
    +[1, 2, 3]

Whitespace separated String Sets could look like this:

    %w<foo bar blah> # creates an array at the moment 
    #w[foo bar blah] # would collide with comments
    $w[foo bar blah] # would collide with sending :[] to $w
    $w{foo bar blah}

    ~%w[foo bar blah] # not really shorter than using an array with strings
    +%w[foo bar balh] # not really shorter than using an array with strings

Maybe it's ok to not have a whitespace separated syntax, I'm just brainstorming here.

The issue with the method approach is that it would create an Array to send the message to first.

I favor the <1, 2, 3> syntax, possibly without the ability to create a whitespace separated version.

I'd be willing to work on a patch not only for MRI but also for JRuby and Rubinius if you would consider this to be useful.
Although I would need help with the parser.
=end



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