+1
I think this is more important than having a general Set syntax as discussed in . Being able to use %ws[foo bar].include?(str) is a double-plus of not creating a new object each time and having O(1) efficiency.

I just thought of something...
In the same way that "str".freeze is optimized to be deduplicated, %w[a b].include?(obj) could be optimized so it becomes equivalent to obj == -"a" || obj == -"b", or something around those lines. This would have the advantage that all existing ruby code that uses this pattern would automatically become faster, without having to convert to a new literal syntax.

Dan0042 (Daniel DeLorme) wrote in #note-3:

I just thought of something...
In the same way that "str".freeze is optimized to be deduplicated, %w[a b].include?(obj) could be optimized so it becomes equivalent to obj == -"a" || obj == -"b", or something around those lines.

That already works on TruffleRuby (and for more than this specific case), it needs a JIT, inlining (also through builtins like #include?) and escape analysis.

[email protected] wrote:

Remaining issues:

• Name? %ws would be the first two character specifier after %. Is it reasonable? Or should we seek another name?
• Frozen? %w returns non frozen array of non frozen strings. How should %ws behave?

How about suffix notation similar to Regexp modifiers?

[ 'foo', 'bar' ]s

Or with ability to specify ordering:

[ 'foo', 'bar' ]os  # ordered set
[ 'foo', 'bar' ]us  # unordered set

Fwiw, I sometimes wish I could use unordered hash to save space:

{ 'foo' => 'bar' }u

And maybe 'f' modifier for frozen strings of values

https://bugs.ruby-lang.org/issues/16994#change-87685