[llvm] [STLExtras] Introduce BinaryPredicateFunctor, [not_]equal_to (PR #175056)

[Jakub Kuderski via llvm-commits]

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@@ -2157,6 +2157,30 @@ template <typename T> bool all_equal(std::initializer_list<T> Values) {
   return all_equal<std::initializer_list<T>>(std::move(Values));
 }
 
+template <typename ValT, typename RefT, typename BinaryPredicate>
+struct BinaryPredicateFunctor {
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kuhar wrote:

If you do want to be able to spell out the type for whatever reason, I suggest framing this as `BindFirst<T, PredT>` with the two members like you have today, and then making the `operator()` variadic and adding CTAD to the class.

https://github.com/llvm/llvm-project/pull/175056