[anfelor]

You might be interested in the FBIP versions of Okasakis datastructures in https://github.com/koka-lang/koka/tree/master/test/perf/sets Most of them only have 'insert' and 'lookup', but they are ~10% faster than Okasakis versions. For red-black trees in particular the fastest implementation is https://github.com/koka-lang/koka/blob/master/test/bench/kok...

[saityi]

I'd missed those -- thank you!