[libcxx-commits] [PATCH] D96084: Revert "Revert "[libc++] [P0879] constexpr std::nth_element, and rewrite its tests.""

[Jordan Rupprecht via Phabricator via libcxx-commits]

rupprecht added a comment.

FWIW, I applied this patch and was able to make it pass this pretty exhaustive test:

    {
    constexpr int kMaxLen = 64;
    for (int len = 1; len < kMaxLen; ++len) {
      int v[kMaxLen];
      for (int i = 0; i < len; ++i)
        v[i] = i;
      T v2[kMaxLen];
      std::copy(v, v + len, v2);
      do {
        for (int n = 0; n < len; ++n) {
          for (int m = 0; m < n; ++m) {
            std::nth_element(Iter(v2), Iter(v2 + m), Iter(v2 + n),
                             std::greater<T>());
            assert(std::is_permutation(v2, v2 + len, v));
            // No element to m's left is less than m.
            for (int i = 0; i < m; ++i) {
              assert(!(v2[i] < v2[m]));
            }
            // No element to m's right is greater than m.
            for (int i = m; i < n; ++i) {
              assert(!(v2[i] > v2[m]));
            }
          }
        }
      } while (std::next_permutation(Iter(v2), Iter(v2 + len)));
    }
  }


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96084/new/

https://reviews.llvm.org/D96084