https://issues.dlang.org/show_bug.cgi?id=13936
--- Comment #18 from Dicebot <pub...@dicebot.lv> --- Some quick notes from a very quick look: > I think we shouldn't care about non-equivalence relations This is something I simply can't accept. groupBy is not a specialized linear algebra thing - it is a quite common utility that will be widely used and widely misused. In fact the reason why non-equivalence implementation has become default in second PR was exactly that some of first attempts of bearophile to experiment with predicate quickly triggered the infinite empty range behavior. I don't thing it is an acceptable for default implementation at all. Some of proposed implementation ideas make lot of sense but I feel very strong about two points: 1) non-equivalence relation support must be default groupBy behavior 2) more efficient versions should be enabled by CT argument as opposed to new function name - it is very hard to invent short names that make sense here (it can still forward to separate private implementation) --
