boost/mpl/inherit.hpp

0001
0002 #if !defined(BOOST_PP_IS_ITERATING)
0003
0004 ///// header body
0005
0006 #ifndef BOOST_MPL_INHERIT_HPP_INCLUDED
0007 #define BOOST_MPL_INHERIT_HPP_INCLUDED
0008
0009 // Copyright Aleksey Gurtovoy 2001-2004
0010 //
0011 // Distributed under the Boost Software License, Version 1.0.
0012 // (See accompanying file LICENSE_1_0.txt or copy at
0013 // http://www.boost.org/LICENSE_1_0.txt)
0014 //
0015 // See http://www.boost.org/libs/mpl for documentation.
0016
0017 // $Id$
0018 // $Date$
0019 // $Revision$
0020
0021 #if !defined(BOOST_MPL_PREPROCESSING_MODE)
0022 #   include <boost/mpl/empty_base.hpp>
0023 #   include <boost/mpl/aux_/na_spec.hpp>
0024 #   include <boost/mpl/aux_/lambda_support.hpp>
0025 #endif
0026
0027 #include <boost/mpl/aux_/config/use_preprocessed.hpp>
0028
0029 #if !defined(BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS) \
0030     && !defined(BOOST_MPL_PREPROCESSING_MODE)
0031
0032 #   define BOOST_MPL_PREPROCESSED_HEADER inherit.hpp
0033 #   include <boost/mpl/aux_/include_preprocessed.hpp>
0034
0035 #else
0036
0037 #   include <boost/mpl/limits/arity.hpp>
0038 #   include <boost/mpl/aux_/preprocessor/params.hpp>
0039 #   include <boost/mpl/aux_/preprocessor/default_params.hpp>
0040 #   include <boost/mpl/aux_/preprocessor/enum.hpp>
0041 #   include <boost/mpl/aux_/config/ctps.hpp>
0042 #   include <boost/mpl/aux_/config/dtp.hpp>
0043
0044 #   include <boost/preprocessor/iterate.hpp>
0045 #   include <boost/preprocessor/dec.hpp>
0046 #   include <boost/preprocessor/cat.hpp>
0047
0048 namespace boost { namespace mpl {
0049
0050 // 'inherit<T1,T2,..,Tn>' metafunction; returns an unspecified class type
0051 // produced by public derivation from all metafunction's parameters
0052 // (T1,T2,..,Tn), except the parameters of 'empty_base' class type;
0053 // regardless the position and number of 'empty_base' parameters in the
0054 // metafunction's argument list, derivation from them is always a no-op;
0055 // for instance:
0056 //      inherit<her>::type == her
0057 //      inherit<her,my>::type == struct unspecified : her, my {};
0058 //      inherit<empty_base,her>::type == her
0059 //      inherit<empty_base,her,empty_base,empty_base>::type == her
0060 //      inherit<her,empty_base,my>::type == struct unspecified : her, my {};
0061 //      inherit<empty_base,empty_base>::type == empty_base
0062
0063 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
0064
0065 template<
0066       typename BOOST_MPL_AUX_NA_PARAM(T1)
0067     , typename BOOST_MPL_AUX_NA_PARAM(T2)
0068     >
0069 struct inherit2
0070     : T1, T2
0071 {
0072     typedef inherit2 type;
0073     BOOST_MPL_AUX_LAMBDA_SUPPORT(2, inherit2, (T1,T2))
0074 };
0075
0076 template< typename T1 >
0077 struct inherit2<T1,empty_base>
0078 {
0079     typedef T1 type;
0080     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (T1,empty_base))
0081 };
0082
0083 template< typename T2 >
0084 struct inherit2<empty_base,T2>
0085 {
0086     typedef T2 type;
0087     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (empty_base,T2))
0088 };
0089
0090 // needed to disambiguate the previous two in case when both
0091 // T1 and T2 == empty_base
0092 template<>
0093 struct inherit2<empty_base,empty_base>
0094 {
0095     typedef empty_base type;
0096     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2, inherit2, (empty_base,empty_base))
0097 };
0098
0099 #else
0100
0101 namespace aux {
0102
0103 template< bool C1, bool C2 >
0104 struct inherit2_impl
0105 {
0106     template< typename Derived, typename T1, typename T2 > struct result_
0107         : T1, T2
0108     {
0109         typedef Derived type_;
0110     };
0111 };
0112
0113 template<>
0114 struct inherit2_impl<false,true>
0115 {
0116     template< typename Derived, typename T1, typename T2 > struct result_
0117         : T1
0118     {
0119         typedef T1 type_;
0120     };
0121 };
0122
0123 template<>
0124 struct inherit2_impl<true,false>
0125 {
0126     template< typename Derived, typename T1, typename T2 > struct result_
0127         : T2
0128     {
0129         typedef T2 type_;
0130     };
0131 };
0132
0133 template<>
0134 struct inherit2_impl<true,true>
0135 {
0136     template< typename Derived, typename T1, typename T2 > struct result_
0137     {
0138         typedef T1 type_;
0139     };
0140 };
0141
0142 } // namespace aux
0143
0144 template<
0145       typename BOOST_MPL_AUX_NA_PARAM(T1)
0146     , typename BOOST_MPL_AUX_NA_PARAM(T2)
0147     >
0148 struct inherit2
0149     : aux::inherit2_impl<
0150           is_empty_base<T1>::value
0151         , is_empty_base<T2>::value
0152         >::template result_< inherit2<T1,T2>,T1,T2 >
0153 {
0154     typedef typename inherit2::type_ type;
0155     BOOST_MPL_AUX_LAMBDA_SUPPORT(2, inherit2, (T1,T2))
0156 };
0157
0158 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
0159
0160 BOOST_MPL_AUX_NA_SPEC(2, inherit2)
0161
0162 #define BOOST_PP_ITERATION_PARAMS_1 \
0163     (3,(3, BOOST_MPL_LIMIT_METAFUNCTION_ARITY, <boost/mpl/inherit.hpp>))
0164 #include BOOST_PP_ITERATE()
0165
0166 }}
0167
0168 #endif // BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
0169 #endif // BOOST_MPL_INHERIT_HPP_INCLUDED
0170
0171 ///// iteration
0172
0173 #else
0174 #define n_ BOOST_PP_FRAME_ITERATION(1)
0175
0176 template<
0177       BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, na)
0178     >
0179 struct BOOST_PP_CAT(inherit,n_)
0180     : inherit2<
0181           typename BOOST_PP_CAT(inherit,BOOST_PP_DEC(n_))<
0182               BOOST_MPL_PP_PARAMS(BOOST_PP_DEC(n_), T)
0183             >::type
0184         , BOOST_PP_CAT(T,n_)
0185         >
0186 {
0187     BOOST_MPL_AUX_LAMBDA_SUPPORT(
0188           n_
0189         , BOOST_PP_CAT(inherit,n_)
0190         , (BOOST_MPL_PP_PARAMS(n_, T))
0191         )
0192 };
0193
0194 BOOST_MPL_AUX_NA_SPEC(n_, BOOST_PP_CAT(inherit,n_))
0195
0196 #if n_ == BOOST_MPL_LIMIT_METAFUNCTION_ARITY
0197 /// primary template
0198 template<
0199       BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, empty_base)
0200     >
0201 struct inherit
0202     : BOOST_PP_CAT(inherit,n_)<BOOST_MPL_PP_PARAMS(n_, T)>
0203 {
0204 };
0205
0206 // 'na' specialization
0207 template<>
0208 struct inherit< BOOST_MPL_PP_ENUM(5, na) >
0209 {
0210     template<
0211 #if !defined(BOOST_MPL_CFG_NO_DEFAULT_PARAMETERS_IN_NESTED_TEMPLATES)
0212           BOOST_MPL_PP_DEFAULT_PARAMS(n_, typename T, empty_base)
0213 #else
0214           BOOST_MPL_PP_PARAMS(n_, typename T)
0215 #endif
0216         >
0217     struct apply
0218         : inherit< BOOST_MPL_PP_PARAMS(n_, T) >
0219     {
0220     };
0221 };
0222
0223 BOOST_MPL_AUX_NA_SPEC_LAMBDA(n_, inherit)
0224 BOOST_MPL_AUX_NA_SPEC_ARITY(n_, inherit)
0225 BOOST_MPL_AUX_NA_SPEC_TEMPLATE_ARITY(n_, n_, inherit)
0226 #endif
0227
0228 #undef n_
0229 #endif // BOOST_PP_IS_ITERATING