Feature #16992

Sets: officially ordered

Added by marcandre (Marc-Andre Lafortune) 7 months ago. Updated 5 months ago.

Target version:


Officially, set elements have uncertain order. This predades when Hash started being ordered (Ruby 1.9.0, Xmas 2007). Sets have since been de-facto insertion-ordered. FYI, in those 13 years, there have been about 70 commits to lib/set.rb.

I have the impression that a non-negligible amount of code in the wild rely on sets being ordered, at least under most circumstances. I feel that this should be officialized.

If sets are truly unordered, then why do we hesitate to make an optimization of & and |:

See also:

Related issues

Related to Ruby master - Feature #16989: Sets: need ♥️Assignedknu (Akinori MUSHA)Actions

Updated by marcandre (Marc-Andre Lafortune) 7 months ago

Updated by Eregon (Benoit Daloze) 5 months ago

+1 from me. Hash if officially ordered.
Making Set unordered would likely break many things.
In practice I would think many Set usages already assume it ordered.
Similar to what I said in

Having unordered elements does not feel Ruby-like, it introduces non-determinism in things as simple as #each.

If super high performance is wanted and being unordered helps, then using a separate class or external gem for that makes sense I think.

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