[libcxx-commits] [libcxx] [libc++][functional] Implement `not_fn<NTTP>` (PR #86133)

[A. Jiang via libcxx-commits]

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@@ -48,6 +50,27 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto not_fn(_Fn&& __f) {
 
 #endif // _LIBCPP_STD_VER >= 17
 
+#if _LIBCPP_STD_VER >= 26
+
+template <auto _Fn>
+struct __nttp_not_fn_t {
+  template <class... _Args>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const
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frederick-vs-ja wrote:

 `volatile` values can be rejected by not using `static`, but this doesn't seem worthwhile... See [[func.require]/4](https://eel.is/c++draft/func.require#4) and [LWG4007](https://cplusplus.github.io/LWG/issue4007).

https://github.com/llvm/llvm-project/pull/86133