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typelevel / algebra

Experimental project to lay out basic algebra type classes
https://typelevel.org/algebra/
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Use diff instead of -- for set difference #134

Closed rklaehn closed 8 years ago

rklaehn commented 8 years ago

At least in case of scala.collection.immutable.HashSet, diff is a tree/tree operation, whereas -- removes all elements of rhs from lhs one by one. So diff is much more efficient.

I did this change (tree/tree operations) to s.c.i.HashSet for 2.11. I also think that it would be a good idea to have xor defined in s.c.i.Set for 2.12.

https://github.com/scala/scala/blob/v2.11.7/src/library/scala/collection/immutable/HashSet.scala#L1

TomasMikula commented 8 years ago

I wrote the code with --. I didn't know it's not the same as diff. Thanks!

:+1:

rklaehn commented 8 years ago

Really, -- should just call diff in HashSet. But we did not dare to do it because of backwards compatibility in some really weird cases :-(