Add FromStr impl for NonZero types
This is a WIP implementation because I do have some questions regarding the solution.
Somebody should ping the lang team on this I guess.
Please see the annotations on the code for more details.
Closes#58604
Implement specialized nth_back() for Box and Windows.
Hi there, this is my first pull request to rust :-)
I started implementing some specializations for DoubleEndedIterator::nth_back() and these are the first two. The problem has been discussed in #54054 and nth_back() is tracked in #56995.
I'm stuck with the next implementation so I though I do a PR for the ones I'm confident with to get some feedback.
Simplify Iterator::{min, max}
This PR simplifies the `select_fold1` helper method used to implmement `Iterator::{min, min_by, min_by_key, max, max_by, max_by_key}` by removing the projection argument, which was only used by the implementations of `min_by_key` and `max_by_key`.
I also added tests to ensure that the stability as mentioned in the comments of `min` and `max` is preserved, and fixed the `iter::{bench_max, bench_max_by_key}` benchmarks which the compiler presumably was able to collapse into closed-form expressions. None of the benchmark results were impacted, I suspect their generated assembly didn't change.
RangeInclusive internal iteration performance improvement.
Specialize `Iterator::try_fold` and `DoubleEndedIterator::try_rfold` to improve code generation in all internal iteration scenarios.
This changes brings the performance of internal iteration with `RangeInclusive` on par with the performance of iteration with `Range`:
- Single conditional jump in hot loop,
- Unrolling and vectorization,
- And even Closed Form substitution.
Unfortunately, it only applies to internal iteration. Despite various attempts at stream-lining the implementation of `next` and `next_back`, LLVM has stubbornly refused to optimize external iteration appropriately, leaving me with a choice between:
- The current implementation, for which Closed Form substitution is performed, but which uses 2 conditional jumps in the hot loop when optimization fail.
- An implementation using a `is_done` boolean, which uses 1 conditional jump in the hot loop when optimization fail, allowing unrolling and vectorization, but for which Closed Form substitution fails.
In the absence of any conclusive evidence as to which usecase matters most, and with no assurance that the lack of Closed Form substitution is not indicative of other optimizations being foiled, there is no way
to pick one implementation over the other, and thus I defer to the statu quo as far as `next` and `next_back` are concerned.
Add signed num::NonZeroI* types
Multiple people have asked for them in https://github.com/rust-lang/rust/issues/49137. Given that the unsigned ones already exist, they are very easy to add and not an additional maintenance burden.
Multiple people have asked for them, in
https://github.com/rust-lang/rust/issues/49137.
Given that the unsigned ones already exist,
they are very easy to add and not an additional maintenance burden.
Add unstable Iterator::copied()
Initially suggested at https://github.com/bluss/rust-itertools/pull/289, however the maintainers of itertools suggested this may be better of in a standard library.
The intent of `copied` is to avoid accidentally cloning iterator elements after doing a code refactoring which causes a structure to be no longer `Copy`. This is a relatively common pattern, as it can be seen by calling `rg --pcre2 '[.]map[(][|](?:(\w+)[|] [*]\1|&(\w+)[|] \2)[)]'` on Rust main repository. Additionally, many uses of `cloned` actually want to simply `Copy`, and changing something to be no longer copyable may introduce unnoticeable performance penalty.
Also, this makes sense because the standard library includes `[T].copy_from_slice` to pair with `[T].clone_from_slice`.
This also adds `Option::copied`, because it makes sense to pair it with `Iterator::copied`. I don't think this feature is particularly important, but it makes sense to update `Option` along with `Iterator` for consistency.
