[ceph.git] / ceph / src / boost / libs / type_traits / doc / is_abstract.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_abstract is_abstract]
   template <class T>
   struct is_abstract : public __tof {};
  
__inherit If T is a (possibly cv-qualified) abstract type then inherits from 
__true_type, otherwise inherits from __false_type.  

__std_ref 10.3.

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

__compat The compiler must support DR337 (as of April 2005: GCC 3.4, VC++ 7.1 (and later),
 Intel C++ 7 (and later), and Comeau 4.3.2).
Otherwise behaves the same as __is_polymorphic; 
this is the "safe fallback position" for which polymorphic types are always 
regarded as potentially abstract.  The macro BOOST_NO_IS_ABSTRACT is used to 
signify that the implementation is buggy, users should check for this in their 
own code if the "safe fallback" is not suitable for their particular use-case.

__examples

[:Given: `class abc{ virtual ~abc() = 0; };` ]

[:`is_abstract<abc>` inherits from `__true_type`.]

[:`is_abstract<abc>::type` is the type `__true_type`.]

[:`is_abstract<abc const>::value` is an integral constant 
expression that evaluates to /true/.]

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

[endsect]
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_abstract is_abstract]
	9	template <class T>
	10	struct is_abstract : public __tof {};
	11
	12	__inherit If T is a (possibly cv-qualified) abstract type then inherits from
	13	__true_type, otherwise inherits from __false_type.
	14
	15	__std_ref 10.3.
	16
	17	__header ` #include <boost/type_traits/is_abstract.hpp>` or ` #include <boost/type_traits.hpp>`
	18
	19	__compat The compiler must support DR337 (as of April 2005: GCC 3.4, VC++ 7.1 (and later),
	20	Intel C++ 7 (and later), and Comeau 4.3.2).
	21	Otherwise behaves the same as __is_polymorphic;
	22	this is the "safe fallback position" for which polymorphic types are always
	23	regarded as potentially abstract. The macro BOOST_NO_IS_ABSTRACT is used to
	24	signify that the implementation is buggy, users should check for this in their
	25	own code if the "safe fallback" is not suitable for their particular use-case.
	26
	27	__examples
	28
	29	[:Given: `class abc{ virtual ~abc() = 0; };` ]
	30
	31	[:`is_abstract<abc>` inherits from `__true_type`.]
	32
	33	[:`is_abstract<abc>::type` is the type `__true_type`.]
	34
	35	[:`is_abstract<abc const>::value` is an integral constant
	36	expression that evaluates to /true/.]
	37
	38	[:`is_abstract<T>::value_type` is the type `bool`.]
	39
	40	[endsect]
	41