P1679 string contains

[Wim Leflere (WimLeflere)]

C++23 string contains implementation

Paper: https://wg21.link/P1679R3
Draft issue: cplusplus/draft#4328
Draft PR: cplusplus/draft#4373

[Miya Natsuhara (mnatsuhara)]

Thank you for your work in this PR! However, I'd like to note that we won't be able to review this PR for a while, as the relevant issue #1450 says:

Note: We're still working on finishing C++20. Until we're done with that (and the compiler implements distinct /std:c++20 and /std:c++latest options), we won't be able to review PRs for C++23 features.

[Wim Leflere (WimLeflere)]

My implementation is based on the starts_with/ends_with implementation.

I was wondering why the const char* function overload is noexcept.
constexpr bool ends_with(const _Elem* const _Right) const noexcept /* strengthened */

While this is explicitly not the case in the standard.

[Stephan T. Lavavej (StephanTLavavej)]

The Standard historically avoided marking non-throwing but precondition-ful functions as noexcept. (The idea was that certain implementations might want to detect and report precondition violations by throwing an exception.) We often "strengthen" such functions to be noexcept in our implementation, with a comment (this is allowed by the Standard). Recently, the Library Working Group has changed its mind about this convention, although the entire Standard hasn't been updated accordingly yet.

[Daniel Marshall (SuperWig)]

Could be worth adding the explanation of the noexcept strengthening in the wiki.

[Daniel Marshall (SuperWig)]

Seems like Stephan T. Lavavej (@StephanTLavavej) missed one

This PR needs to merge main and resolve a conflict in yvals_core.h.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks, this looks great! My apologies for the delay in reviewing your PR (due in part to C++20 marathon exhaustion and summer vacations). All I found were minor issues, so to save time I'll push changes (mainly adding constexpr for the basic_string overloads and updating a test accordingly) and move this to Final Review. After a second maintainer can double-check everything, we'll able to merge this for VS 2022 17.0 Preview 3.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks for adding this feature to the Standard and implementing it here - and congratulations on your first microsoft/STL commit! 😸 🎉 🚀 This will ship in VS 2022 17.0 Preview 3.