92 lines
2.6 KiB
C++
92 lines
2.6 KiB
C++
// Boost.TypeErasure library
|
|
//
|
|
// Copyright 2011 Steven Watanabe
|
|
//
|
|
// 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)
|
|
//
|
|
// $Id: relaxed.hpp 83252 2013-03-02 19:58:42Z steven_watanabe $
|
|
|
|
#ifndef BOOST_TYPE_ERASURE_RELAXED_HPP_INCLUDED
|
|
#define BOOST_TYPE_ERASURE_RELAXED_HPP_INCLUDED
|
|
|
|
#include <boost/mpl/vector.hpp>
|
|
#include <boost/mpl/bool.hpp>
|
|
#include <boost/mpl/is_sequence.hpp>
|
|
#include <boost/mpl/find_if.hpp>
|
|
#include <boost/mpl/not.hpp>
|
|
#include <boost/mpl/end.hpp>
|
|
#include <boost/type_traits/is_same.hpp>
|
|
|
|
namespace boost {
|
|
namespace type_erasure {
|
|
|
|
template<class T>
|
|
struct is_relaxed;
|
|
|
|
namespace detail {
|
|
|
|
template<class T>
|
|
struct is_relaxed_impl :
|
|
::boost::mpl::not_<
|
|
typename ::boost::is_same<
|
|
typename ::boost::mpl::find_if<
|
|
T,
|
|
::boost::type_erasure::is_relaxed< ::boost::mpl::_1>
|
|
>::type,
|
|
typename ::boost::mpl::end<T>::type
|
|
>::type
|
|
>::type
|
|
{};
|
|
|
|
}
|
|
|
|
/**
|
|
* This special concept enables various useful default behavior that
|
|
* makes @ref any act like an ordinary object. By default @ref any
|
|
* forwards all operations to the underlying type, and provides only
|
|
* the operations that are specified in its @c Concept.
|
|
*
|
|
* In detail, @ref relaxed enables the following:
|
|
* - A raw value can be assigned to an @ref any. This will replace
|
|
* the value stored by the @ref any. (But note that if @ref assignable
|
|
* is present, it takes priority.)
|
|
* - copy assignment of @ref any uses the copy constructor if it can't
|
|
* use @ref assignable (either because @ref assignable is missing,
|
|
* or because the stored types do not match).
|
|
* - default construction of @ref any is allowed and creates a null any.
|
|
* - @ref equality_comparable "equality_comparable": If the types do not
|
|
* match, it will return false.
|
|
* - @ref less_than_comparable "less_than_comparable": If the types do not
|
|
* match, the ordering will be according to
|
|
* @c std::type_info::before.
|
|
* - if the arguments to any other function do not match, it will throw
|
|
* a @ref bad_function_call exception instead of having undefined
|
|
* behavior.
|
|
*/
|
|
struct relaxed : ::boost::mpl::vector0<> {};
|
|
|
|
/**
|
|
* A metafunction indicating whether @c Concept
|
|
* includes @ref relaxed.
|
|
*/
|
|
template<class Concept>
|
|
struct is_relaxed :
|
|
::boost::mpl::eval_if< ::boost::mpl::is_sequence<Concept>,
|
|
::boost::type_erasure::detail::is_relaxed_impl<Concept>,
|
|
::boost::mpl::false_
|
|
>::type
|
|
{};
|
|
|
|
/** INTERNAL ONLY */
|
|
template<>
|
|
struct is_relaxed< ::boost::type_erasure::relaxed> :
|
|
::boost::mpl::true_
|
|
{};
|
|
|
|
}
|
|
}
|
|
|
|
#endif
|