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Feature #16992

Sets: officially ordered

Added by marcandre (Marc-Andre Lafortune) 4 months ago. Updated about 2 months ago.

Status:
Open
Priority:
Normal
Target version:
-
[ruby-core:98967]

Description

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 |: https://bugs.ruby-lang.org/issues/15281

See also: https://bugs.ruby-lang.org/issues/14069


Related issues

Related to Ruby master - Feature #16989: Sets: need ♥️Assignedknu (Akinori MUSHA)Actions
#1

Updated by marcandre (Marc-Andre Lafortune) 4 months ago

Updated by Eregon (Benoit Daloze) about 2 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 https://bugs.ruby-lang.org/issues/15281#note-9

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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