# Overview
As a disclaimer, this is my first PR to LLVM and while I've tried to
ensure I've followed the LLVM and libc++ contributing guidelines,
there's probably a good chance I missed something. If I have, just let
me know and I'll try to correct it as soon as I can.
This PR implements `std::ranges::iota` and
`std::ranges::out_value_result` outlined in
[P2440r1](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2440r1.html).
As outlined in the paper above, I've:
- Implemented `out_value_result` and added to `<algorithm>`
- Added `out_value_result`, `iota_result`, and two overloads of `iota`
to `std::ranges` in `<numeric>`
- Updated the version macro `__cpp_lib_ranges_iota` in `<version>`
I've also added tests for `ranges::iota` and `ranges::out_value_result`.
Lastly, I added those structs to the appropriate module files.
Partially implements #105184
EDIT: Forgot to mention in the original post, thanks to @hawkinsw for
taking a look at a preliminary version of this PR!
# TODOs
- [x] Updating the range [status
doc](https://github.com/jamesETsmith/llvm-project/blob/main/libcxx/docs/Status/RangesMajorFeatures.csv)
- [x] Ensure all comments from https://reviews.llvm.org/D121436 are
addressed here
- [X] EDIT (I'll do this in a separate PR). ~~I'm open to implementing
the rest of P2440r1 (`ranges::shift_left` and `ranges::shift_right`) if
that's ok, I just wanted to get feedback on `ranges::iota` first~~
- [x] I've been having trouble building the modules locally and want to
make sure that's working properly
Closes: #134060
Notable things in this commit:
* refactors `__indirect_binary_left_foldable`, making it slightly
different (but equivalent) to _`indirect-binary-left-foldable`_, which
improves readability (a [patch to the Working Paper][patch] was made)
* omits `__cpo` namespace, since it is not required for implementing
niebloids (a cleanup should happen in 2024)
* puts tests ensuring invocable robustness and dangling correctness
inside the correctness testing to ensure that the algorithms' results
are still correct
[patch]: https://github.com/cplusplus/draft/pull/6734
When we ship LLVM 16, <ranges> won't be considered experimental anymore.
We might as well do this sooner rather than later.
Differential Revision: https://reviews.llvm.org/D132151
