Issue #5478 has been updated by Alexey Muranov. What about simply { :a, :b, :c } ? It should be obvious to Ruby that this is not a hash. In fact, how about specifying that internally Set is a form of Hash, and to have a lossless conversion Set->Hash->Set? I do not know the current implementation of Set, but the most natural in my opinion would be the following: { :a => nil, :b => nil, :c => nil } # is the set of { :a, :b, :c }. How about making Ruby interpret { :a, :b, :c => 1 } as an alternative form of { :a => nil, :b => nil, :c => 1}, and view Set as a simplified Hash, where all values are nil? That is, make ruby understand that { :a, :b, :c => 1 } is a hash, but { :a, :b, :c } is a Set (which inherits from Hash). ---------------------------------------- Feature #5478: import Set into core, add syntax http://redmine.ruby-lang.org/issues/5478 Author: 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 -- http://redmine.ruby-lang.org