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rust-itertools / itertools

Extra iterator adaptors, iterator methods, free functions, and macros.
https://docs.rs/itertools/
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Const generics iterator candidates #547

Open conradludgate opened 3 years ago

conradludgate commented 3 years ago

Discussed in #546 where I've written an alternative to tuple_combinations, array_combinations which is an iterator that outputs [T; N]. This feature requires const generics which were introduced in Rust 1.51. It was suggested that we can bump the MSRV in a major release (ie itertools 0.11) but it would be sensible to add more features along side.

This crate uses a lot of tuples where arrays make more sense. Tuples are good when you have multiple types (eg cartesian product or zip) but when you have a collection of the same type, a slice/vec/array makes more sense.

Here's a list of functions that seem to qualify using arrays:

These all work on a single iterator over the single I::Item type, and since these use tuples, the number of elements is known at compile time, making them perfect for using arrays instead of tuples.

scottmcm commented 3 years ago

Note that things like array_windows for iterators are under discussion for iterators in std, see conversations like https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Iterator.3A.3A.7Bpairwise.2C.20windows.7D/near/224587771

As I understand it std didn't want the tuple ones because of the extra trait complications in the interface, but with const generics available the array ones might be able to live there instead of here.

Plecra commented 9 months ago

Could this be added and gated on rust 1.51? That'd maintain backwards compatibility without any problem

Philippe-Cholet commented 9 months ago

@Plecra We use 1.43.1 at the moment but will move to 1.51 at some point and use const generics, no doubt. I don't think there is a discussion about when we will do it but I suppose after #755 (well underway) and #844 (not started).

TonalidadeHidrica commented 1 month ago

Now that #959 is merged, can we also start to merge other https://github.com/rust-itertools/itertools/labels/const-generics PRs? I really want to see array_windows and many other possible array-based features which simplify my code.

jswrenn commented 1 month ago

Yes! I'm going to try to get some of these merged in the coming weeks.