Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
A pointer to a function, a pointer to member function, a pointer to member data, or a class type whose objects can appear immediately to the left of a function call operator.
& a_free_function
& a_class::a_static_member_function
& a_class::a_nonstatic_data_member
& a_class::a_nonstatic_member_function
std::less<int>()
// using namespace boost;
bind(std::less<int>(), _1, 5)
lambda::_1 += lambda::_2;
fusion::make_fused_function_object(std::less<int>())