Thanks! No, I don't have benchmarks. My guess is that FSet is not as fast as the Clojure collections, which use a newer data structure (Phil Bagwell's Hash Ar

Thanks! No, I don't have benchmarks. My guess is that FSet is not as fast as the Clojure collections, which use a newer data structure (Phil Bagwell's Hash Array-Mapped Trie) that I didn't know about when I wrote FSet. -- Um, that's for sets and maps. For seqs (functional vectors), I'm not sure but I think the Clojure data structure is very similar to FSet's. I think the odds that FSet is significantly faster than Clojure are small, though I suppose it's worth checking. For the domain I work in -- compilers and static analysis -- the additional overhead of functional collections has only rarely been an issue in practice. It's different from numerics, though, in that a lot of our collections are maps keyed by nonnumeric objects; the time spent hashing the object and testing it for equality with other objects is relatively much larger than when the keys are simply integers, and therefore the time spent traversing the data structure itself is a smaller part of the total. I concede that designing functional collections for use in high-performance numeric work is a harder problem, though I still suspect that solutions may exist. See my reply to your other post.