Is it possible to adapt member functions using concept maps?
No. Only non-member (free) functions and operators written as non-member (free) functions can be adapted using concept maps. Scott Meyers has advised C++ programmers to prefer non-member (free) functions over member functions in his 2003 article, “How Non-Member Functions Improve Encapsulation.” The same advice applies to concepts. There are several reasons for this design decision, but the main reason boils down to a major syntactic problem with expressing adapted member functions in concept maps. The way one writes a member function requirement in a concept is the same way that one writes a definition of a member function outside of the class. For example, here’s a concept that requires a member function swap: concept MemSwappable
