[libcxx-commits] [PATCH] D93557: [libc++] [P0879] constexpr std::nth_element, and rewrite its tests.

[Arthur O'Dwyer via Phabricator via libcxx-commits]

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This patch is more than just adding the `constexpr` keyword, because the old code relied on `goto`, and `goto` is not constexpr-friendly. Refactor to eliminate `goto`, and then mark it as constexpr in C++20.

I freely admit that the name `__nth_element_partloop` is bad; I couldn't find any better name because I don't really know what this loop is doing, conceptually. Vice versa, I think `__nth_element_find_guard` has a decent name.

Now the only one we're still missing from P0879 is `sort`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93557

Files:
  libcxx/include/algorithm
  libcxx/test/std/algorithms/alg.sorting/alg.nth.element/nth_element.pass.cpp
  libcxx/test/std/algorithms/alg.sorting/alg.nth.element/nth_element_comp.pass.cpp

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