1 
2 #ifndef BOOST_MPL_AUX_PUSH_FRONT_IMPL_HPP_INCLUDED
3 #define BOOST_MPL_AUX_PUSH_FRONT_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_front_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_front_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_front_arg {};
29 
30 // agurt 05/feb/04: no default implementation; the stub definition is needed
31 // to enable the default 'has_push_front' implementation below
32 
33 template< typename Tag >
34 struct push_front_impl
35 {
36     template< typename Sequence, typename T > struct apply
37     {
38         // should be instantiated only in the context of 'has_push_front_impl';
39         // if you've got an assert here, you are requesting a 'push_front'
40         // specialization that doesn't exist.
41         BOOST_MPL_ASSERT_MSG(
42               ( boost::is_same< T, has_push_front_arg >::value )
43             , REQUESTED_PUSH_FRONT_SPECIALIZATION_FOR_SEQUENCE_DOES_NOT_EXIST
44             , ( Sequence )
45             );
46     };
47 };
48 
49 template< typename Tag >
50 struct has_push_front_impl
51 {
52     template< typename Seq > struct apply
53 #if !defined(BOOST_MPL_CFG_NO_NESTED_FORWARDING)
54         : aux::has_type< push_front< Seq, has_push_front_arg > >
55     {
56 #else
57     {
58         typedef aux::has_type< push_front< Seq, has_push_front_arg > > type;
59         BOOST_STATIC_CONSTANT(bool, value =
60               (aux::has_type< push_front< Seq, has_push_front_arg > >::value)
61             );
62 #endif
63     };
64 };
65 
66 BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(2, push_front_impl)
67 BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(1, has_push_front_impl)
68 
69 }}
70 
71 #endif // BOOST_MPL_AUX_PUSH_FRONT_IMPL_HPP_INCLUDED
72