Boost_1_39_0/boost/numeric/conversion/detail/meta.hpp

   1 //  (c) Copyright Fernando Luis Cacciola Carballal 2000-2004
   2 //  Use, modification, and distribution is subject to the Boost Software
   3 //  License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   4 //  http://www.boost.org/LICENSE_1_0.txt)
   5
   6 //  See library home page at http://www.boost.org/libs/numeric/conversion
   7 //
   8 // Contact the author at: fernando_cacciola@hotmail.com
   9 //
  10 #ifndef BOOST_NUMERIC_CONVERSION_DETAIL_META_FLC_12NOV2002_HPP
  11 #define BOOST_NUMERIC_CONVERSION_DETAIL_META_FLC_12NOV2002_HPP
  12
  13 #include "boost/type_traits/remove_cv.hpp"
  14
  15 #include "boost/mpl/if.hpp"
  16 #include "boost/mpl/eval_if.hpp"
  17 #include "boost/mpl/equal_to.hpp"
  18 #include "boost/mpl/not.hpp"
  19 #include "boost/mpl/and.hpp"
  20 #include "boost/mpl/bool.hpp"
  21 #include "boost/mpl/identity.hpp"
  22
  23 namespace boost { namespace numeric { namespace convdetail
  24 {
  25    template< class T1, class T2>
  26    struct equal_to
  27    {
  28    #if !defined(__BORLANDC__)
  29
  30        enum { x = ( BOOST_MPL_AUX_VALUE_WKND(T1)::value == BOOST_MPL_AUX_VALUE_WKND(T2)::value ) };
  31
  32        BOOST_STATIC_CONSTANT(bool, value = x);
  33
  34        typedef mpl::bool_<value> type;
  35
  36    #else
  37
  38        BOOST_STATIC_CONSTANT(bool, value = (
  39              BOOST_MPL_AUX_VALUE_WKND(T1)::value
  40                == BOOST_MPL_AUX_VALUE_WKND(T2)::value
  41            ));
  42
  43        typedef mpl::bool_<(
  44              BOOST_MPL_AUX_VALUE_WKND(T1)::value
  45                == BOOST_MPL_AUX_VALUE_WKND(T2)::value
  46            )> type;
  47    #endif
  48    };
  49
  50 // Metafunction:
  51   //
  52   //   ct_switch4<Value,Case0Val,Case1Val,Case2Val,Case0Type,Case1Type,Case2Type,DefaultType>::type
  53   //
  54   // {Value,Case(X)Val} are Integral Constants (such as: mpl::int_<>)
  55   // {Case(X)Type,DefaultType} are arbitrary types. (not metafunctions)
  56   //
  57   // Returns Case(X)Type if Val==Case(X)Val; DefaultType otherwise.
  58   //
  59   template<class Value,
  60            class Case0Val,
  61            class Case1Val,
  62            class Case2Val,
  63            class Case0Type,
  64            class Case1Type,
  65            class Case2Type,
  66            class DefaultType
  67           >
  68   struct ct_switch4
  69   {
  70     typedef mpl::identity<Case0Type> Case0TypeQ ;
  71     typedef mpl::identity<Case1Type> Case1TypeQ ;
  72
  73     typedef equal_to<Value,Case0Val> is_case0 ;
  74     typedef equal_to<Value,Case1Val> is_case1 ;
  75     typedef equal_to<Value,Case2Val> is_case2 ;
  76
  77     typedef mpl::if_<is_case2,Case2Type,DefaultType> choose_2_3Q ;
  78     typedef mpl::eval_if<is_case1,Case1TypeQ,choose_2_3Q> choose_1_2_3Q ;
  79
  80     typedef typename
  81       mpl::eval_if<is_case0,Case0TypeQ,choose_1_2_3Q>::type
  82         type ;
  83   } ;
  84
  85
  86
  87
  88   // Metafunction:
  89   //
  90   //   for_both<expr0,expr1,TT,TF,FT,FF>::type
  91   //
  92   // {exp0,expr1} are Boolean Integral Constants
  93   // {TT,TF,FT,FF} are aribtrary types. (not metafunctions)
  94   //
  95   // According to the combined boolean value of 'expr0 && expr1', selects the corresponding type.
  96   //
  97   template<class expr0, class expr1, class TT, class TF, class FT, class FF>
  98   struct for_both
  99   {
 100     typedef mpl::identity<TF> TF_Q ;
 101     typedef mpl::identity<TT> TT_Q ;
 102
 103     typedef typename mpl::not_<expr0>::type not_expr0 ;
 104     typedef typename mpl::not_<expr1>::type not_expr1 ;
 105
 106     typedef typename mpl::and_<expr0,expr1>::type     caseTT ;
 107     typedef typename mpl::and_<expr0,not_expr1>::type caseTF ;
 108     typedef typename mpl::and_<not_expr0,expr1>::type caseFT ;
 109
 110     typedef mpl::if_<caseFT,FT,FF>                    choose_FT_FF_Q ;
 111     typedef mpl::eval_if<caseTF,TF_Q,choose_FT_FF_Q> choose_TF_FT_FF_Q ;
 112
 113     typedef typename mpl::eval_if<caseTT,TT_Q,choose_TF_FT_FF_Q>::type type ;
 114   } ;
 115
 116 } } } // namespace boost::numeric::convdetail
 117
 118 #endif
 119
 120