Issue #5478 has been updated by Alexey Muranov. Jos Backus wrote: > How would one represent an empty Set? > '{}' can't be used as it would be ambiguous. Good point. Need to think about this. I would be in favor of using `{}` for the empty set and `Hash::new`, or `Hash[]`, or `{}.to_hash` for the empty hash. To keep partial compatibility, Set can convert itself to Hash if a `#[]` or `#[]=` method is called on it. Actually, can it? Can an object replace itself with an object of another class in Ruby? Also, `{}` can be an object of some common ancestor class of Hash and Set, if this can help. I think it should be possible to use a single class as both Set and Hash, but having set methods and hash methods both defined on the same object somehow seems strange to me. ---------------------------------------- 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