pointer_to_unary_function

template<class Arg, class Result>
    class pointer_to_unary_function
        : public unary_function<Arg, Result> {
public:
    explicit pointer_to_unary_function(Result (*pf)(Arg));
    Result operator()(const Arg x) const;
    };

The template class stores a copy of pf. It defines its member function operator() as returning (*pf)(x).