is_pointer.qbk

来自「Boost provides free peer-reviewed portab」· QBK 代码 · 共 46 行

[/ 
  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_pointer is_pointer]
   template <class T>
   struct is_pointer : public __tof {};
  
__inherit If T is a (possibly cv-qualified) pointer type (includes function pointers, 
but excludes pointers to members) then inherits from __true_type, 
otherwise inherits from __false_type.

__std_ref 3.9.2p2 and 8.3.1.

__header ` #include <boost/type_traits/is_pointer.hpp>` or ` #include <boost/type_traits.hpp>`

__examples

[:`is_pointer<int*>` inherits from `__true_type`.]

[:`is_pointer<char* const>::type` is the type `__true_type`.]

[:`is_pointer<int (*)(long)>::value` is an integral constant 
expression that evaluates to /true/.]

[:`is_pointer<int (MyClass::*)(long)>::value` is an integral constant 
expression that evaluates to /false/.]

[:`is_pointer<int (MyClass::*)>::value` is an integral constant 
expression that evaluates to /false/.]

[:`is_pointer<T>::value_type` is the type `bool`.]

[important `is_pointer` detects "real" pointer types only, and /not/ smart pointers.
Users should not specialise `is_pointer` for smart pointer types, as doing so may cause
Boost (and other third party) code to fail to function correctly.
Users wanting a trait to detect smart pointers should create their own. 
However, note that there is no way in general to auto-magically detect smart pointer types, 
so such a trait would have to be partially specialised for each supported smart pointer type.]

[endsect]