projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | [/ |
| 2 | Copyright 2007 John Maddock. | |
| 3 | Distributed under the Boost Software License, Version 1.0. | |
| 4 | (See accompanying file LICENSE_1_0.txt or copy at | |
| 5 | http://www.boost.org/LICENSE_1_0.txt). | |
| 6 | ] | |
| 7 | ||
| 8 | [section:is_function is_function] | |
| 9 | ||
| 10 | template <class T> | |
| 11 | struct is_function : public __tof {}; | |
| 12 | ||
| 13 | __inherit If T is a (possibly cv-qualified) function type then inherits from __true_type, | |
| 14 | otherwise inherits from __false_type. Note that this template does not detect /pointers | |
| 15 | to functions/, or /references to functions/, these are detected by __is_pointer and | |
| 16 | __is_reference respectively: | |
| 17 | ||
| 18 | typedef int f1(); // f1 is of function type. | |
| 19 | typedef int (*f2)(); // f2 is a pointer to a function. | |
| 20 | typedef int (&f3)(); // f3 is a reference to a function. | |
| 21 | ||
| 22 | __std_ref 3.9.2p1 and 8.3.5. | |
| 23 | ||
| 24 | [all_compilers] | |
| 25 | ||
| 26 | __header ` #include <boost/type_traits/is_function.hpp>` or ` #include <boost/type_traits.hpp>` | |
| 27 | ||
| 28 | __examples | |
| 29 | ||
| 30 | [:`is_function<int (void)>` inherits from `__true_type`.] | |
| 31 | ||
| 32 | [:`is_function<long (double, int)>::type` is the type `__true_type`.] | |
| 33 | ||
| 34 | [:`is_function<long (double, int)>::value` is an integral constant | |
| 35 | expression that evaluates to /true/.] | |
| 36 | ||
| 37 | [:`is_function<long (*)(double, int)>::value` is an integral constant | |
| 38 | expression that evaluates to /false/: the argument in this case is a pointer type, | |
| 39 | not a function type.] | |
| 40 | ||
| 41 | [:`is_function<long (&)(double, int)>::value` is an integral constant | |
| 42 | expression that evaluates to /false/: the argument in this case is a | |
| 43 | reference to a function, not a function type.] | |
| 44 | ||
| 45 | [:`is_function<long (MyClass::*)(double, int)>::value` is an integral constant | |
| 46 | expression that evaluates to /false/: the argument in this case is a pointer | |
| 47 | to a member function.] | |
| 48 | ||
| 49 | [:`is_function<T>::value_type` is the type `bool`.] | |
| 50 | ||
| 51 | [tip Don't confuse function-types with pointers to functions: | |
| 52 | ||
| 53 | `typedef int f(double);` | |
| 54 | ||
| 55 | defines a function type, | |
| 56 | ||
| 57 | `f foo;` | |
| 58 | ||
| 59 | declares a prototype for a function of type `f`, | |
| 60 | ||
| 61 | `f* pf = foo;` | |
| 62 | ||
| 63 | `f& fr = foo;` | |
| 64 | ||
| 65 | declares a pointer and a reference to the function `foo`. | |
| 66 | ||
| 67 | If you want to detect whether some type is a pointer-to-function then use: | |
| 68 | ||
| 69 | `__is_function<__remove_pointer<T>::type>::value && __is_pointer<T>::value` | |
| 70 | ||
| 71 | or for pointers to member functions you can just use | |
| 72 | __is_member_function_pointer directly. | |
| 73 | ] | |
| 74 | ||
| 75 | [endsect] | |
| 76 | ||
| 77 |