Hi all, I recently noticed that lookup for IntMap favours searches that can fast-fail - if instead we are in a situation where lookups are mostly successful, then this can be wasteful (see this issue for details: https://github.com/haskell/containers/issues/794). Since both versions are useful, it would be best to offer users both variants. I wondered if people on this list had any suggestions for a name for the new function? David Feuer also wondered which of these two behaviours should be the default. My inclination is for it to be the current version which fails faster (this also guarantees no unfortunate regressions) but it would be useful to run more substantial real-world benchmarks to figure that out (if anyone has any suggestions then do let me know). Best wishes, Callan