1 
2 #ifndef BOOST_MPL_AUX_PUSH_BACK_IMPL_HPP_INCLUDED
3 #define BOOST_MPL_AUX_PUSH_BACK_IMPL_HPP_INCLUDED
4 
5 // Copyright Aleksey Gurtovoy 2000-2008
6 //
7 // Distributed under the Boost Software License, Version 1.0.
8 // (See accompanying file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // See http://www.boost.org/libs/mpl for documentation.
12 
13 // $Id: push_back_impl.hpp 55679 2009-08-20 07:50:16Z agurtovoy $
14 // $Date: 2009-08-20 00:50:16 -0700 (Thu, 20 Aug 2009) $
15 // $Revision: 55679 $
16 
17 #include <boost/mpl/push_back_fwd.hpp>
18 #include <boost/mpl/assert.hpp>
19 #include <boost/mpl/aux_/has_type.hpp>
20 #include <boost/mpl/aux_/traits_lambda_spec.hpp>
21 #include <boost/mpl/aux_/config/forwarding.hpp>
22 #include <boost/mpl/aux_/config/static_constant.hpp>
23 
24 #include <boost/type_traits/is_same.hpp>
25 
26 namespace boost { namespace mpl {
27 
28 struct has_push_back_arg {};
29 
30 // agurt 05/feb/04: no default implementation; the stub definition is needed
31 // to enable the default 'has_push_back' implementation below
32 template< typename Tag >
33 struct push_back_impl
34 {
35     template< typename Sequence, typename T > struct apply
36     {
37         // should be instantiated only in the context of 'has_push_back_impl';
38         // if you've got an assert here, you are requesting a 'push_back'
39         // specialization that doesn't exist.
40         BOOST_MPL_ASSERT_MSG(
41               ( boost::is_same< T, has_push_back_arg >::value )
42             , REQUESTED_PUSH_BACK_SPECIALIZATION_FOR_SEQUENCE_DOES_NOT_EXIST
43             , ( Sequence )
44             );
45     };
46 };
47 
48 template< typename Tag >
49 struct has_push_back_impl
50 {
51     template< typename Seq > struct apply
52 #if !defined(BOOST_MPL_CFG_NO_NESTED_FORWARDING)
53         : aux::has_type< push_back< Seq, has_push_back_arg > >
54     {
55 #else
56     {
57         typedef aux::has_type< push_back< Seq, has_push_back_arg > > type;
58         BOOST_STATIC_CONSTANT(bool, value =
59               (aux::has_type< push_back< Seq, has_push_back_arg > >::value)
60             );
61 #endif
62     };
63 };
64 
65 BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(2, push_back_impl)
66 BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(1, has_push_back_impl)
67 
68 }}
69 
70 #endif // BOOST_MPL_AUX_PUSH_BACK_IMPL_HPP_INCLUDED
71