libs/type_traits/doc/is_function.qbk
[/ Copyright 2007 John Maddock. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt). ] [section:is_function is_function] template <class T> struct is_function : public __tof {}; __inherit If T is a (possibly cv-qualified) function type then inherits from __true_type, otherwise inherits from __false_type. Note that this template does not detect /pointers to functions/, or /references to functions/, these are detected by __is_pointer and __is_reference respectively: typedef int f1(); // f1 is of function type. typedef int (f2*)(); // f2 is a pointer to a function. typedef int (f3&)(); // f3 is a reference to a function. __std_ref 3.9.2p1 and 8.3.5. __header ` #include <boost/type_traits/is_function.hpp>` or ` #include <boost/type_traits.hpp>` __examples [:`is_function<int (void)>` inherits from `__true_type`.] [:`is_function<long (double, int)>::type` is the type `__true_type`.] [:`is_function<long (double, int)>::value` is an integral constant expression that evaluates to /true/.] [:`is_function<long (*)(double, int)>::value` is an integral constant expression that evaluates to /false/: the argument in this case is a pointer type, not a function type.] [:`is_function<long (&)(double, int)>::value` is an integral constant expression that evaluates to /false/: the argument in this case is a reference to a function, not a function type.] [:`is_function<long (MyClass::*)(double, int)>::value` is an integral constant expression that evaluates to /false/: the argument in this case is a pointer to a member function.] [:`is_function<T>::value_type` is the type `bool`.] [tip Don't confuse function-types with pointers to functions: `typedef int f(double);` defines a function type, `f foo;` declares a prototype for a function of type `f`, `f* pf = foo;` `f& fr = foo;` declares a pointer and a reference to the function `foo`. If you want to detect whether some type is a pointer-to-function then use: `__is_function<__remove_pointer<T>::type>::value && __is_pointer<T>::value` or for pointers to member functions you can just use __is_member_function_pointer directly. ] [endsect]