What are transparent comparators?

Question

In C++14, associative containers seem to have changed from C++11 – [associative.reqmts]/13 says:

The member function templates find

Answer 1

Stephan T Lavavej talks about problems where the compiler keeps creating temporaries, and how his proposal of transparent operator functors will solve this in c++1y

GoingNative 2013 - Dont help the Compiler (at about the hour mark)