boost/mpl/inherit.hpp

   1
   2 #if !defined(BOOST_PP_IS_ITERATING)
   3
   4 ///// header body
   5
   6 #ifndef BOOST_MPL_INHERIT_HPP_INCLUDED
   7 #define BOOST_MPL_INHERIT_HPP_INCLUDED
   8
   9 // Copyright Aleksey Gurtovoy 2001-2004
  10 //
  11 // Distributed under the Boost Software License, Version 1.0.
  12 // (See accompanying file LICENSE_1_0.txt or copy at
  13 // http://www.boost.org/LICENSE_1_0.txt)
  14 //
  15 // See http://www.boost.org/libs/mpl for documentation.
  16
  17 // $Id: inherit.hpp 49267 2008-10-11 06:19:02Z agurtovoy $
  18 // $Date: 2008-10-10 23:19:02 -0700 (Fri, 10 Oct 2008) $
  19 // $Revision: 49267 $
  20
  21 #if !defined(BOOST_MPL_PREPROCESSING_MODE)
  22 #   include <boost/mpl/empty_base.hpp>
  23 #   include <boost/mpl/aux_/na_spec.hpp>
  24 #   include <boost/mpl/aux_/lambda_support.hpp>
  25 #endif
  26
  27 #include <boost/mpl/aux_/config/use_preprocessed.hpp>
  28
  29 #if !defined(BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS) \
  30     && !defined(BOOST_MPL_PREPROCESSING_MODE)
  31
  32 #   define BOOST_MPL_PREPROCESSED_HEADER inherit.hpp
  33 #   include <boost/mpl/aux_/include_preprocessed.hpp>
  34
  35 #else
  36
  37 #   include <boost/mpl/limits/arity.hpp>
  38 #   include <boost/mpl/aux_/preprocessor/params.hpp>
  39 #   include <boost/mpl/aux_/preprocessor/default_params.hpp>
  40 #   include <boost/mpl/aux_/preprocessor/enum.hpp>
  41 #   include <boost/mpl/aux_/config/ctps.hpp>
  42 #   include <boost/mpl/aux_/config/dtp.hpp>
  43
  44 #   include <boost/preprocessor/iterate.hpp>
  45 #   include <boost/preprocessor/dec.hpp>
  46 #   include <boost/preprocessor/cat.hpp>
  47
  48 namespace boost { namespace mpl {
  49
  50 // 'inherit<T1,T2,..,Tn>' metafunction; returns an unspecified class type
  51 // produced by public derivation from all metafunction's parameters
  52 // (T1,T2,..,Tn), except the parameters of 'empty_base' class type;
  53 // regardless the position and number of 'empty_base' parameters in the
  54 // metafunction's argument list, derivation from them is always a no-op;
  55 // for instance:
  56 //      inherit<her>::type == her
  57 //      inherit<her,my>::type == struct unspecified : her, my {};
  58 //      inherit<empty_base,her>::type == her
  59 //      inherit<empty_base,her,empty_base,empty_base>::type == her
  60 //      inherit<her,empty_base,my>::type == struct unspecified : her, my {};
  61 //      inherit<empty_base,empty_base>::type == empty_base
  62
  63 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  64
  65 template<
  66       typename BOOST_MPL_AUX_NA_PARAM(T1)
  67     , typename BOOST_MPL_AUX_NA_PARAM(T2)
  68     >
  69 struct inherit2
  70     : T1, T2
  71 {
  72     typedef inherit2 type;
  73     BOOST_MPL_AUX_LAMBDA_SUPPORT(2, inherit2, (T1,T2))
  74 };
  75
  76 template< typename T1 >
  77 struct inherit2<T1,empty_base>
  78 {
  79     typedef T1 type;
  80     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (T1,empty_base))
  81 };
  82
  83 template< typename T2 >
  84 struct inherit2<empty_base,T2>
  85 {
  86     typedef T2 type;
  87     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (empty_base,T2))
  88 };
  89
  90 // needed to disambiguate the previous two in case when both
  91 // T1 and T2 == empty_base
  92 template<>
  93 struct inherit2<empty_base,empty_base>
  94 {
  95     typedef empty_base type;
  96     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (empty_base,empty_base))
  97 };
  98
  99 #else
 100
 101 namespace aux {
 102
 103 template< bool C1, bool C2 >
 104 struct inherit2_impl
 105 {
 106     template< typename Derived, typename T1, typename T2 > struct result_
 107         : T1, T2
 108     {
 109         typedef Derived type_;
 110     };
 111 };
 112
 113 template<>
 114 struct inherit2_impl<false,true>
 115 {
 116     template< typename Derived, typename T1, typename T2 > struct result_
 117         : T1
 118     {
 119         typedef T1 type_;
 120     };
 121 };
 122
 123 template<>
 124 struct inherit2_impl<true,false>
 125 {
 126     template< typename Derived, typename T1, typename T2 > struct result_
 127         : T2
 128     {
 129         typedef T2 type_;
 130     };
 131 };
 132
 133 template<>
 134 struct inherit2_impl<true,true>
 135 {
 136     template< typename Derived, typename T1, typename T2 > struct result_
 137     {
 138         typedef T1 type_;
 139     };
 140 };
 141
 142 } // namespace aux
 143
 144 template<
 145       typename BOOST_MPL_AUX_NA_PARAM(T1)
 146     , typename BOOST_MPL_AUX_NA_PARAM(T2)
 147     >
 148 struct inherit2
 149     : aux::inherit2_impl<
 150           is_empty_base<T1>::value
 151         , is_empty_base<T2>::value
 152         >::template result_< inherit2<T1,T2>,T1,T2 >
 153 {
 154     typedef typename inherit2::type_ type;
 155     BOOST_MPL_AUX_LAMBDA_SUPPORT(2, inherit2, (T1,T2))
 156 };
 157
 158 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 159
 160 BOOST_MPL_AUX_NA_SPEC(2, inherit2)
 161
 162 #define BOOST_PP_ITERATION_PARAMS_1 \
 163     (3,(3, BOOST_MPL_LIMIT_METAFUNCTION_ARITY, <boost/mpl/inherit.hpp>))
 164 #include BOOST_PP_ITERATE()
 165
 166 }}
 167
 168 #endif // BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
 169 #endif // BOOST_MPL_INHERIT_HPP_INCLUDED
 170
 171 ///// iteration
 172
 173 #else
 174 #define n_ BOOST_PP_FRAME_ITERATION(1)
 175
 176 template<
 177       BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, na)
 178     >
 179 struct BOOST_PP_CAT(inherit,n_)
 180     : inherit2<
 181           typename BOOST_PP_CAT(inherit,BOOST_PP_DEC(n_))<
 182               BOOST_MPL_PP_PARAMS(BOOST_PP_DEC(n_), T)
 183             >::type
 184         , BOOST_PP_CAT(T,n_)
 185         >
 186 {
 187     BOOST_MPL_AUX_LAMBDA_SUPPORT(
 188           n_
 189         , BOOST_PP_CAT(inherit,n_)
 190         , (BOOST_MPL_PP_PARAMS(n_, T))
 191         )
 192 };
 193
 194 BOOST_MPL_AUX_NA_SPEC(n_, BOOST_PP_CAT(inherit,n_))
 195
 196 #if n_ == BOOST_MPL_LIMIT_METAFUNCTION_ARITY
 197 /// primary template
 198 template<
 199       BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, empty_base)
 200     >
 201 struct inherit
 202     : BOOST_PP_CAT(inherit,n_)<BOOST_MPL_PP_PARAMS(n_, T)>
 203 {
 204 };
 205
 206 // 'na' specialization
 207 template<>
 208 struct inherit< BOOST_MPL_PP_ENUM(5, na) >
 209 {
 210     template<
 211 #if !defined(BOOST_MPL_CFG_NO_DEFAULT_PARAMETERS_IN_NESTED_TEMPLATES)
 212           BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, empty_base)
 213 #else
 214           BOOST_MPL_PP_PARAMS(n_, typename T)
 215 #endif
 216         >
 217     struct apply
 218         : inherit< BOOST_MPL_PP_PARAMS(n_, T) >
 219     {
 220     };
 221 };
 222
 223 BOOST_MPL_AUX_NA_SPEC_LAMBDA(n_, inherit)
 224 BOOST_MPL_AUX_NA_SPEC_ARITY(n_, inherit)
 225 BOOST_MPL_AUX_NA_SPEC_TEMPLATE_ARITY(n_, n_, inherit)
 226 #endif
 227
 228 #undef n_
 229 #endif // BOOST_PP_IS_ITERATING