is_stateless.qbk

来自「Boost provides free peer-reviewed portab」· QBK 代码 · 共 41 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_stateless is_stateless]
   template <class T>
   struct is_stateless : public __tof {};
  
__inherit Ff T is a stateless type then inherits from __true_type, otherwise
from __false_type.

Type T must be a complete type.

A stateless type is a type that has no storage and whose constructors and 
destructors are trivial. That means that `is_stateless` only inherits from 
__true_type if the following expression is `true`:

   ::boost::has_trivial_constructor<T>::value
   && ::boost::has_trivial_copy<T>::value
   && ::boost::has_trivial_destructor<T>::value
   && ::boost::is_class<T>::value
   && ::boost::is_empty<T>::value

__std_ref 3.9p10.

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

__compat If the compiler does not support partial-specialization of class templates, 
then this template can not be used with function types.

Without some (as yet unspecified) help from the compiler, is_stateless will never 
report that a class or struct is stateless; this is always safe, 
if possibly sub-optimal.  Currently (May 2005) only MWCW 9 and Visual C++ 8 have the necessary 
compiler __intrinsics to make this template work automatically.

[endsect]