Feature #6589: Set#rehash

• Status: Closed
• Assignee: knu (Akinori MUSHA)
• Target version: 2.6

[marcandre (Marc-Andre Lafortune)]

There should be a way to rehash a Set.

s = Set.new([[]])
s.first << 1
# s.rehash # Does not exist!
s.include? [1] # => false, want true

See also:

http://stackoverflow.com/questions/10992423/is-this-expected-behaviour-for-a-set-of-arrays-in-ruby
http://stackoverflow.com/questions/10361400/deleting-a-modified-object-from-a-set-in-a-no-op

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned

[yhara (Yutaka HARA)]

• Target version changed from 2.0.0 to 2.6

[marcandre (Marc-Andre Lafortune)]

Comment about this trivial but needed feature would be appreciated.

[headius (Charles Nutter)]

Is it specified that Set must be hashtable-based forever? There are alternate ways to implement a Set.

[marcandre (Marc-Andre Lafortune)]

headius (Charles Nutter) wrote:

Is it specified that Set must be hashtable-based forever? There are alternate ways to implement a Set.

Alternate ways of implementing Set with check/insertion in O(1) that would also work if structures change without a rehash functionality?

In any case, the documentation states that "Set uses Hash as storage", but more importantly that "The equality of each couple of elements is determined according to Object#eql? and Object#hash".

[knu (Akinori MUSHA)]

Actually, an undocumented "feature" is that Set does not support an element being modified once it is added.

Maybe we should "clarify" that in the document, or add such a method that recalculates identities of elements. I'm yet to decide which, and the name we could give it.

• rehash (let's be honest)
• reset (re-set the set)
• sync
• ...

[knu (Akinori MUSHA)]

• Status changed from Assigned to Feedback

I added some notes to the rdoc in r42265.

[marcandre (Marc-Andre Lafortune)]

• Related to Bug #12970: == Equality of recursive sets fails added

[knu (Akinori MUSHA)]

• Status changed from Feedback to Closed

Applied in changeset trunk|r60360.

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Add Set#reset

This method resets the internal state of a set after modification to
existing elements, reindexing and deduplicating them. [Feature #6589]