boost/type_traits/has_minus.hpp

0001 //  (C) Copyright 2009-2011 Frederic Bron.
0002 //
0003 //  Use, modification and distribution are subject to the Boost Software License,
0004 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0005 //  http://www.boost.org/LICENSE_1_0.txt).
0006 //
0007 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
0008
0009 #ifndef BOOST_TT_HAS_MINUS_HPP_INCLUDED
0010 #define BOOST_TT_HAS_MINUS_HPP_INCLUDED
0011
0012 #include <boost/config.hpp>
0013 #include <boost/type_traits/detail/config.hpp>
0014
0015 // cannot include this header without getting warnings of the kind:
0016 // gcc:
0017 //    warning: value computed is not used
0018 //    warning: comparison between signed and unsigned integer expressions
0019 // msvc:
0020 //    warning C4018: '<' : signed/unsigned mismatch
0021 //    warning C4244: '+=' : conversion from 'double' to 'char', possible loss of data
0022 //    warning C4547: '*' : operator before comma has no effect; expected operator with side-effect
0023 //    warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)
0024 //    warning C4804: '<' : unsafe use of type 'bool' in operation
0025 //    warning C4805: '==' : unsafe mix of type 'bool' and type 'char' in operation
0026 // cannot find another implementation -> declared as system header to suppress these warnings.
0027 #if defined(__GNUC__)
0028 #   pragma GCC system_header
0029 #elif defined(BOOST_MSVC)
0030 #   pragma warning ( push )
0031 #   pragma warning ( disable : 4018 4244 4547 4800 4804 4805 4913 4133)
0032 #   if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000)
0033 #       pragma warning ( disable : 6334)
0034 #   endif
0035 #endif
0036
0037 #if defined(BOOST_TT_HAS_ACCURATE_BINARY_OPERATOR_DETECTION)
0038
0039 #include <boost/type_traits/integral_constant.hpp>
0040 #include <boost/type_traits/make_void.hpp>
0041 #include <boost/type_traits/is_convertible.hpp>
0042 #include <boost/type_traits/is_void.hpp>
0043 #include <boost/type_traits/add_reference.hpp>
0044 #include <boost/type_traits/remove_pointer.hpp>
0045 #include <boost/type_traits/remove_reference.hpp>
0046 #include <utility>
0047
0048 namespace boost
0049 {
0050
0051    namespace binary_op_detail {
0052
0053       struct dont_care;
0054
0055       template <class T, class U, class Ret, class = void>
0056       struct has_minus_ret_imp : public boost::false_type {};
0057
0058       template <class T, class U, class Ret>
0059       struct has_minus_ret_imp<T, U, Ret, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() - std::declval<typename add_reference<U>::type>())>::type>
0060          : public boost::integral_constant<bool, ::boost::is_convertible<decltype(std::declval<typename add_reference<T>::type>() - std::declval<typename add_reference<U>::type>()), Ret>::value> {};
0061
0062       template <class T, class U, class = void >
0063       struct has_minus_void_imp : public boost::false_type {};
0064
0065       template <class T, class U>
0066       struct has_minus_void_imp<T, U, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() - std::declval<typename add_reference<U>::type>())>::type>
0067          : public boost::integral_constant<bool, ::boost::is_void<decltype(std::declval<typename add_reference<T>::type>() - std::declval<typename add_reference<U>::type>())>::value> {};
0068
0069       template <class T, class U, class = void>
0070       struct has_minus_dc_imp : public boost::false_type {};
0071
0072       template <class T, class U>
0073       struct has_minus_dc_imp<T, U, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() - std::declval<typename add_reference<U>::type>())>::type>
0074          : public boost::true_type {};
0075
0076       template <class T, class U, class Ret>
0077       struct has_minus_ret_filter : public boost::binary_op_detail::has_minus_ret_imp <T, U, Ret> {};
0078       template <class T, class U>
0079       struct has_minus_ret_filter<T, U, void> : public boost::binary_op_detail::has_minus_void_imp <T, U> {};
0080       template <class T, class U>
0081       struct has_minus_ret_filter<T, U, boost::binary_op_detail::dont_care> : public boost::binary_op_detail::has_minus_dc_imp <T, U> {};
0082
0083       template <class T, class U, class Ret, bool b>
0084       struct has_minus_void_ptr_filter : public boost::binary_op_detail::has_minus_ret_filter <T, U, Ret> {};
0085       template <class T, class U, class Ret>
0086       struct has_minus_void_ptr_filter<T, U, Ret, true> : public boost::false_type {};
0087
0088    }
0089
0090    template <class T, class U = T, class Ret = boost::binary_op_detail::dont_care>
0091    struct has_minus :
0092       public boost::binary_op_detail::has_minus_void_ptr_filter<
0093          T, U, Ret,
0094          boost::is_void<typename remove_pointer<typename remove_reference<T>::type>::type>::value
0095          || boost::is_void<typename remove_pointer<typename remove_reference<U>::type>::type>::value> {};
0096
0097
0098 }
0099
0100 #else
0101
0102
0103 #define BOOST_TT_TRAIT_NAME has_minus
0104 #define BOOST_TT_TRAIT_OP -
0105 #define BOOST_TT_FORBIDDEN_IF\
0106    (\
0107       /* Lhs==pointer and Rhs==fundamental and Rhs!=integral */\
0108       (\
0109          ::boost::is_pointer< Lhs_noref >::value && \
0110          ::boost::is_fundamental< Rhs_nocv >::value && \
0111          (!  ::boost::is_integral< Rhs_noref >::value )\
0112       ) || \
0113       /* Lhs==void* and (Rhs==fundamental or Rhs==pointer) */\
0114       (\
0115          ::boost::is_pointer< Lhs_noref >::value && \
0116          ::boost::is_void< Lhs_noptr >::value && \
0117          ( \
0118             ::boost::is_fundamental< Rhs_nocv >::value || \
0119             ::boost::is_pointer< Rhs_noref >::value\
0120           )\
0121       ) || \
0122       /* Rhs==void* and (Lhs==fundamental or Lhs==pointer) */\
0123       (\
0124          ::boost::is_pointer< Rhs_noref >::value && \
0125          ::boost::is_void< Rhs_noptr >::value && \
0126          (\
0127             ::boost::is_fundamental< Lhs_nocv >::value || \
0128             ::boost::is_pointer< Lhs_noref >::value\
0129           )\
0130       ) ||\
0131       /* Lhs=fundamental and Rhs=pointer */\
0132       (\
0133          ::boost::is_fundamental< Lhs_nocv >::value && \
0134          ::boost::is_pointer< Rhs_noref >::value\
0135       ) ||\
0136       /* two different pointers */\
0137       (\
0138          ::boost::is_pointer< Lhs_noref >::value && \
0139          ::boost::is_pointer< Rhs_noref >::value && \
0140          (!  ::boost::is_same< Lhs_nocv, Rhs_nocv >::value )\
0141       )\
0142       )
0143
0144 #define BOOST_TT_FORBIDDEN_IF_NEW (boost::is_void<typename remove_pointer<typename boost::remove_reference<T>::type>::type>::value || boost::is_void<typename remove_pointer<typename boost::remove_reference<U>::type>::type>::value)
0145
0146 #include <boost/type_traits/detail/has_binary_operator.hpp>
0147
0148 #undef BOOST_TT_TRAIT_NAME
0149 #undef BOOST_TT_TRAIT_OP
0150 #undef BOOST_TT_FORBIDDEN_IF
0151
0152 #endif
0153
0154 #if defined(BOOST_MSVC)
0155 #   pragma warning (pop)
0156 #endif
0157
0158 #endif