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


nobu (Nobuyoshi Nakada) wrote:
> =begin
> Seems off-topic.
> 
>  h1 = {a: 1}; h2 = {b: 2}
>  def foo(name: 'unknown', **rest) name; end
>  foo **h1, **h2, name: "foo" #=> "foo"
> =end

Ok nobu, thanks for the idea.  Then back to the topic.  If combining `Hash` and `Set` is somehow unfeasible, the question stays about the literal notation for `Set`, and if using `{1, 2, 3}`, how to distinguish the empty set from the empty hash.

I can propose `{ - }` for the empty set.

I think it would be even better to use `{}` for the empty set and `{=>}` or `{:}` for the empty hash, but this would be incompatible with the current use.

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Feature #5478: import Set into core, add syntax
https://bugs.ruby-lang.org/issues/5478#change-28658

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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