boost/mpl/sequence_tag.hpp

   1
   2 #ifndef BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
   3 #define BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
   4
   5 // Copyright Aleksey Gurtovoy 2000-2004
   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 // $Id$
  14 // $Date$
  15 // $Revision$
  16
  17 #include <boost/mpl/sequence_tag_fwd.hpp>
  18 #include <boost/mpl/aux_/has_tag.hpp>
  19 #include <boost/mpl/aux_/has_begin.hpp>
  20 #include <boost/mpl/aux_/na_spec.hpp>
  21 #include <boost/mpl/aux_/is_msvc_eti_arg.hpp>
  22 #include <boost/mpl/aux_/config/eti.hpp>
  23 #include <boost/mpl/aux_/yes_no.hpp>
  24 #include <boost/mpl/aux_/config/workaround.hpp>
  25
  26 namespace boost { namespace mpl {
  27
  28 // agurt, 27/nov/02: have to use a simplistic 'sequence_tag' implementation
  29 // on MSVC to avoid dreadful "internal structure overflow" error
  30 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) \
  31     || defined(BOOST_MPL_CFG_NO_HAS_XXX)
  32
  33 template<
  34       typename BOOST_MPL_AUX_NA_PARAM(Sequence)
  35     >
  36 struct sequence_tag
  37 {
  38     typedef typename Sequence::tag type;
  39 };
  40
  41 #elif BOOST_WORKAROUND(BOOST_MSVC, == 1300)
  42
  43 // agurt, 07/feb/03: workaround for what seems to be MSVC 7.0-specific ETI issue
  44
  45 namespace aux {
  46
  47 template< bool >
  48 struct sequence_tag_impl
  49 {
  50     template< typename Sequence > struct result_
  51     {
  52         typedef typename Sequence::tag type;
  53     };
  54 };
  55
  56 template<>
  57 struct sequence_tag_impl<false>
  58 {
  59     template< typename Sequence > struct result_
  60     {
  61         typedef int type;
  62     };
  63 };
  64
  65 } // namespace aux
  66
  67 template<
  68       typename BOOST_MPL_AUX_NA_PARAM(Sequence)
  69     >
  70 struct sequence_tag
  71     : aux::sequence_tag_impl< !aux::is_msvc_eti_arg<Sequence>::value >
  72         ::template result_<Sequence>
  73 {
  74 };
  75
  76 #else
  77
  78 namespace aux {
  79
  80 template< bool has_tag_, bool has_begin_ >
  81 struct sequence_tag_impl
  82 {
  83     // agurt 24/nov/02: MSVC 6.5 gets confused in 'sequence_tag_impl<true>'
  84     // specialization below, if we name it 'result_' here
  85     template< typename Sequence > struct result2_;
  86 };
  87
  88 #   define AUX_CLASS_SEQUENCE_TAG_SPEC(has_tag, has_begin, result_type) \
  89 template<> struct sequence_tag_impl<has_tag,has_begin> \
  90 { \
  91     template< typename Sequence > struct result2_ \
  92     { \
  93         typedef result_type type; \
  94     }; \
  95 }; \
  96 /**/
  97
  98 AUX_CLASS_SEQUENCE_TAG_SPEC(true, true, typename Sequence::tag)
  99 AUX_CLASS_SEQUENCE_TAG_SPEC(true, false, typename Sequence::tag)
 100 AUX_CLASS_SEQUENCE_TAG_SPEC(false, true, nested_begin_end_tag)
 101 AUX_CLASS_SEQUENCE_TAG_SPEC(false, false, non_sequence_tag)
 102
 103 #   undef AUX_CLASS_SEQUENCE_TAG_SPEC
 104
 105 } // namespace aux
 106
 107 template<
 108       typename BOOST_MPL_AUX_NA_PARAM(Sequence)
 109     >
 110 struct sequence_tag
 111     : aux::sequence_tag_impl<
 112           ::boost::mpl::aux::has_tag<Sequence>::value
 113         , ::boost::mpl::aux::has_begin<Sequence>::value
 114         >::template result2_<Sequence>
 115 {
 116 };
 117
 118 #endif // BOOST_MSVC
 119
 120 BOOST_MPL_AUX_NA_SPEC(1, sequence_tag)
 121
 122 }}
 123
 124 #endif // BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED