Pre-RFC: Add comparator-api for ordered collections

[xxchan]

Wow, the binary-heap-plus crate is interesting, it does almost the same as this pre-RFC, although its motivation is just for flexibility, without considering the runtime generated comparator problem here.

I found its pre-RFC, closed for inactivity. Maybe we can learn from the discussions and propose an official RFC this time! (cc @sekineh

Pre-RFC: BinaryHeap Flexibility

Update (2018-05-17) I published the crate binary-heap-plus for those who need custom ordered heap NOW. https://crates.io/crates/binary-heap-plus FnMut based solution might be better than Compare<T> for RFC inclusion, but it requires some unstable features to be written nicely. I won't (can't) write the FnMut based RFC for the time being because I'm not familiar with the related unstable features. Thanks for all suggestions! Pre-RFC Feature Name: binary_heap_flexivility Start Date: (fill …

BinaryHeap RFC, redux

Last year, @sekineh drafted an RFC and published a prototype crate proposing changing std::BinaryHeap to permit custom (potentially stateful) comparators. The Internals thread was eventually closed for inactivity, and as far as I can tell, the RFC was never proposed on the official RFC repo; @sekineh or anyone else, are you still interested in working on such an RFC? I think this would be a valuable feature.