[Haskell-cafe] Symmetric Difference for Data.Set and Data.IntSet?

[Ben Franksen]

Zemyla wrote:
> Could this be implemented as a primitive? I know it can be made from union
> and difference, or doing toList on both of them, taking the symmetric
> difference, and using fromDistinctAscList on the result, but it'd probably
> be much faster if it could be done natively, like can be done with
> Data.Map.mergeWithKey.

+1

> Alternatively, could we get a merge interface for Set and IntSet roughly
> matching Map and IntMap?
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