boost/mpl/aux_/push_front_impl.hpp

   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