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Remove object_id use in Set#flatten #34

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Remove object_id use in Set#flatten #34

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7 changes: 3 additions & 4 deletions lib/set.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -361,16 +361,15 @@ def to_set(klass = Set, *args, &block)
klass.new(self, *args, &block)
end

def flatten_merge(set, seen = Set.new) # :nodoc:
def flatten_merge(set, seen = Set.new.compare_by_identity) # :nodoc:
set.each { |e|
if e.is_a?(Set)
if seen.include?(e_id = e.object_id)
unless seen.add?(e)
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@amomchilov amomchilov Dec 18, 2023

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There's 3 nice performance wins here:

  • We don't trigger a look up (and potentially an assignment) of an object ID
  • We can do an identity-based look-up, which is faster
  • We combine the include? and add steps into one, saving one hash lookup/comparison.

raise ArgumentError, "tried to flatten recursive Set"
end

seen.add(e_id)
flatten_merge(e, seen)
seen.delete(e_id)
seen.delete(e)
else
add(e)
end
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