williamr@2: 
williamr@2: // Copyright 2000 John Maddock (john@johnmaddock.co.uk)
williamr@2: // Copyright 2000 Jeremy Siek (jsiek@lsc.nd.edu)
williamr@2: // Copyright 1999, 2000 Jaakko J„rvi (jaakko.jarvi@cs.utu.fi)
williamr@2: //
williamr@2: //  Use, modification and distribution are subject to the Boost Software License,
williamr@2: //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
williamr@2: //  http://www.boost.org/LICENSE_1_0.txt).
williamr@2: //
williamr@2: //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
williamr@2: 
williamr@2: #ifndef BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
williamr@2: #define BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
williamr@2: 
williamr@2: #include <boost/type_traits/detail/yes_no_type.hpp>
williamr@2: #include <boost/type_traits/config.hpp>
williamr@2: #include <boost/type_traits/is_array.hpp>
williamr@2: #include <boost/type_traits/add_reference.hpp>
williamr@2: #include <boost/type_traits/ice.hpp>
williamr@2: #include <boost/type_traits/is_arithmetic.hpp>
williamr@2: #include <boost/type_traits/is_void.hpp>
williamr@2: #ifndef BOOST_NO_IS_ABSTRACT
williamr@2: #include <boost/type_traits/is_abstract.hpp>
williamr@2: #endif
williamr@2: 
williamr@2: #if defined(__MWERKS__)
williamr@2: #include <boost/type_traits/is_function.hpp>
williamr@2: #include <boost/type_traits/remove_reference.hpp>
williamr@2: #endif
williamr@2: 
williamr@2: // should be always the last #include directive
williamr@2: #include <boost/type_traits/detail/bool_trait_def.hpp>
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2: // is one type convertable to another?
williamr@2: //
williamr@2: // there are multiple versions of the is_convertible
williamr@2: // template, almost every compiler seems to require its
williamr@2: // own version.
williamr@2: //
williamr@2: // Thanks to Andrei Alexandrescu for the original version of the
williamr@2: // conversion detection technique!
williamr@2: //
williamr@2: 
williamr@2: namespace detail {
williamr@2: 
williamr@2: // MS specific version:
williamr@2: 
williamr@2: #if defined(BOOST_MSVC) && (BOOST_MSVC <= 1300)
williamr@2: 
williamr@2: // This workaround is necessary to handle when From is void
williamr@2: // which is normally taken care of by the partial specialization
williamr@2: // of the is_convertible typename.
williamr@2: using ::boost::type_traits::yes_type;
williamr@2: using ::boost::type_traits::no_type;
williamr@2: 
williamr@2: template< typename From >
williamr@2: struct does_conversion_exist
williamr@2: {
williamr@2:     template< typename To > struct result_
williamr@2:     {
williamr@2:         static no_type BOOST_TT_DECL _m_check(...);
williamr@2:         static yes_type BOOST_TT_DECL _m_check(To);
williamr@2:         static From _m_from;
williamr@2:         enum { value = sizeof( _m_check(_m_from) ) == sizeof(yes_type) };
williamr@2:     };
williamr@2: };
williamr@2: 
williamr@2: template<>
williamr@2: struct does_conversion_exist<void>
williamr@2: {
williamr@2:     template< typename To > struct result_
williamr@2:     {
williamr@2:         enum { value = ::boost::is_void<To>::value };
williamr@2:     };
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl
williamr@2:     : does_conversion_exist<From>::template result_<To>
williamr@2: {
williamr@2: };
williamr@2: 
williamr@2: #elif defined(__BORLANDC__) && (__BORLANDC__ < 0x560)
williamr@2: //
williamr@2: // special version for Borland compilers
williamr@2: // this version breaks when used for some
williamr@2: // UDT conversions:
williamr@2: //
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_impl
williamr@2: {
williamr@2: #pragma option push -w-8074
williamr@2:     // This workaround for Borland breaks the EDG C++ frontend,
williamr@2:     // so we only use it for Borland.
williamr@2:     template <typename T> struct checker
williamr@2:     {
williamr@2:         static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
williamr@2:         static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(T);
williamr@2:     };
williamr@2: 
williamr@2:     static From _m_from;
williamr@2:     static bool const value = sizeof( checker<To>::_m_check(_m_from) )
williamr@2:         == sizeof(::boost::type_traits::yes_type);
williamr@2: #pragma option pop
williamr@2: };
williamr@2: 
williamr@2: #elif defined(__GNUC__) || defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
williamr@2: // special version for gcc compiler + recent Borland versions
williamr@2: // note that this does not pass UDT's through (...)
williamr@2: 
williamr@2: struct any_conversion
williamr@2: {
williamr@2:     template <typename T> any_conversion(const volatile T&);
williamr@2:     template <typename T> any_conversion(T&);
williamr@2: };
williamr@2: 
williamr@2: template <typename T> struct checker
williamr@2: {
williamr@2:     static boost::type_traits::no_type _m_check(any_conversion ...);
williamr@2:     static boost::type_traits::yes_type _m_check(T, int);
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl
williamr@2: {
williamr@2:     static From _m_from;
williamr@2:     static bool const value = sizeof( detail::checker<To>::_m_check(_m_from, 0) )
williamr@2:         == sizeof(::boost::type_traits::yes_type);
williamr@2: };
williamr@2: 
williamr@2: #elif (defined(__EDG_VERSION__) && (__EDG_VERSION__ >= 245) && !defined(__ICL)) \
williamr@2:       || defined(__IBMCPP__) || defined(__HP_aCC)
williamr@2: //
williamr@2: // This is *almost* an ideal world implementation as it doesn't rely
williamr@2: // on undefined behaviour by passing UDT's through (...).
williamr@2: // Unfortunately it doesn't quite pass all the tests for most compilers (sigh...)
williamr@2: // Enable this for your compiler if is_convertible_test.cpp will compile it...
williamr@2: //
williamr@2: // Note we do not enable this for VC7.1, because even though it passes all the
williamr@2: // type_traits tests it is known to cause problems when instantiation occurs
williamr@2: // deep within the instantiation tree :-(
williamr@2: //
williamr@2: struct any_conversion
williamr@2: {
williamr@2:     template <typename T> any_conversion(const volatile T&);
williamr@2:     // we need this constructor to catch references to functions
williamr@2:     // (which can not be cv-qualified):
williamr@2:     template <typename T> any_conversion(T&);
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl
williamr@2: {
williamr@2:     static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion ...);
williamr@2:     static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int);
williamr@2:        static From _m_from;
williamr@2: 
williamr@2:     BOOST_STATIC_CONSTANT(bool, value =
williamr@2:         sizeof( _m_check(_m_from, 0) ) == sizeof(::boost::type_traits::yes_type)
williamr@2:         );
williamr@2: };
williamr@2: 
williamr@2: #elif defined(__DMC__)
williamr@2: 
williamr@2: struct any_conversion
williamr@2: {
williamr@2:     template <typename T> any_conversion(const volatile T&);
williamr@2:     // we need this constructor to catch references to functions
williamr@2:     // (which can not be cv-qualified):
williamr@2:     template <typename T> any_conversion(T&);
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl
williamr@2: {
williamr@2:     // Using '...' doesn't always work on Digital Mars. This version seems to.
williamr@2:     template <class T>
williamr@2:     static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion,  float, T);
williamr@2:     static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int, int);
williamr@2:     static From _m_from;
williamr@2: 
williamr@2:     // Static constants sometime cause the conversion of _m_from to To to be
williamr@2:     // called. This doesn't happen with an enum.
williamr@2:     enum { value =
williamr@2:         sizeof( _m_check(_m_from, 0, 0) ) == sizeof(::boost::type_traits::yes_type)
williamr@2:         };
williamr@2: };
williamr@2: 
williamr@2: #elif defined(__MWERKS__)
williamr@2: // 
williamr@2: // CW works with the technique implemented above for EDG, except when From
williamr@2: // is a function type (or a reference to such a type), in which case
williamr@2: // any_conversion won't be accepted as a valid conversion. We detect this
williamr@2: // exceptional situation and channel it through an alternative algorithm.
williamr@2: //
williamr@2: 
williamr@2: template <typename From, typename To,bool FromIsFunctionRef>
williamr@2: struct is_convertible_basic_impl_aux;
williamr@2: 
williamr@2: struct any_conversion
williamr@2: {
williamr@2:     template <typename T> any_conversion(const volatile T&);
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl_aux<From,To,false /*FromIsFunctionRef*/>
williamr@2: {
williamr@2:     static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion ...);
williamr@2:     static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int);
williamr@2:     static From _m_from;
williamr@2: 
williamr@2:     BOOST_STATIC_CONSTANT(bool, value =
williamr@2:         sizeof( _m_check(_m_from, 0) ) == sizeof(::boost::type_traits::yes_type)
williamr@2:         );
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl_aux<From,To,true /*FromIsFunctionRef*/>
williamr@2: {
williamr@2:     static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
williamr@2:     static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
williamr@2:     static From _m_from;
williamr@2:     BOOST_STATIC_CONSTANT(bool, value =
williamr@2:         sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
williamr@2:         );
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl:
williamr@2:   is_convertible_basic_impl_aux<
williamr@2:     From,To,
williamr@2:     ::boost::is_function<typename ::boost::remove_reference<From>::type>::value
williamr@2:   >
williamr@2: {};
williamr@2: 
williamr@2: #else
williamr@2: 
williamr@2: //
williamr@2: // This version seems to work pretty well for a wide spectrum of compilers,
williamr@2: // however it does rely on undefined behaviour by passing UDT's through (...).
williamr@2: //
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_basic_impl
williamr@2: {
williamr@2:     static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
williamr@2:     static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
williamr@2:     static From _m_from;
williamr@2: #ifdef BOOST_MSVC
williamr@2: #pragma warning(push)
williamr@2: #pragma warning(disable:4244)
williamr@2: #endif
williamr@2:     BOOST_STATIC_CONSTANT(bool, value =
williamr@2:         sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
williamr@2:         );
williamr@2: #ifdef BOOST_MSVC
williamr@2: #pragma warning(pop)
williamr@2: #endif
williamr@2: };
williamr@2: 
williamr@2: #endif // is_convertible_impl
williamr@2: 
williamr@2: #if defined(__DMC__)
williamr@2: // As before, a static constant sometimes causes errors on Digital Mars.
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_impl
williamr@2: {
williamr@2:     typedef typename add_reference<From>::type ref_type;
williamr@2:     enum { value =
williamr@2:         (::boost::type_traits::ice_and<
williamr@2:             ::boost::type_traits::ice_or<
williamr@2:                ::boost::detail::is_convertible_basic_impl<ref_type,To>::value,
williamr@2:                ::boost::is_void<To>::value
williamr@2:             >::value,
williamr@2:             ::boost::type_traits::ice_not<
williamr@2:                ::boost::is_array<To>::value
williamr@2:             >::value
williamr@2:         >::value) };
williamr@2: };
williamr@2: #elif !defined(__BORLANDC__) || __BORLANDC__ > 0x551
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_impl
williamr@2: {
williamr@2:     typedef typename add_reference<From>::type ref_type;
williamr@2:     BOOST_STATIC_CONSTANT(bool, value =
williamr@2:         (::boost::type_traits::ice_and<
williamr@2:             ::boost::type_traits::ice_or<
williamr@2:                ::boost::detail::is_convertible_basic_impl<ref_type,To>::value,
williamr@2:                ::boost::is_void<To>::value
williamr@2:             >::value,
williamr@2:             ::boost::type_traits::ice_not<
williamr@2:                ::boost::is_array<To>::value
williamr@2:             >::value
williamr@2:         >::value)
williamr@2:         );
williamr@2: };
williamr@2: #endif
williamr@2: 
williamr@2: template <bool trivial1, bool trivial2, bool abstract_target>
williamr@2: struct is_convertible_impl_select
williamr@2: {
williamr@2:    template <class From, class To>
williamr@2:    struct rebind
williamr@2:    {
williamr@2:       typedef is_convertible_impl<From, To> type;
williamr@2:    };
williamr@2: };
williamr@2: 
williamr@2: template <>
williamr@2: struct is_convertible_impl_select<true, true, false>
williamr@2: {
williamr@2:    template <class From, class To>
williamr@2:    struct rebind
williamr@2:    {
williamr@2:       typedef true_type type;
williamr@2:    };
williamr@2: };
williamr@2: 
williamr@2: template <>
williamr@2: struct is_convertible_impl_select<false, false, true>
williamr@2: {
williamr@2:    template <class From, class To>
williamr@2:    struct rebind
williamr@2:    {
williamr@2:       typedef false_type type;
williamr@2:    };
williamr@2: };
williamr@2: 
williamr@2: template <>
williamr@2: struct is_convertible_impl_select<true, false, true>
williamr@2: {
williamr@2:    template <class From, class To>
williamr@2:    struct rebind
williamr@2:    {
williamr@2:       typedef false_type type;
williamr@2:    };
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_impl_dispatch_base
williamr@2: {
williamr@2: #if !BOOST_WORKAROUND(__HP_aCC, < 60700)
williamr@2:    typedef is_convertible_impl_select< 
williamr@2:       ::boost::is_arithmetic<From>::value, 
williamr@2:       ::boost::is_arithmetic<To>::value,
williamr@2: #ifndef BOOST_NO_IS_ABSTRACT
williamr@2:       ::boost::is_abstract<To>::value
williamr@2: #else
williamr@2:       false
williamr@2: #endif
williamr@2:    > selector;
williamr@2: #else
williamr@2:    typedef is_convertible_impl_select<false, false, false> selector;
williamr@2: #endif
williamr@2:    typedef typename selector::template rebind<From, To> isc_binder;
williamr@2:    typedef typename isc_binder::type type;
williamr@2: };
williamr@2: 
williamr@2: template <typename From, typename To>
williamr@2: struct is_convertible_impl_dispatch 
williamr@2:    : public is_convertible_impl_dispatch_base<From, To>::type
williamr@2: {};
williamr@2: 
williamr@2: //
williamr@2: // Now add the full and partial specialisations
williamr@2: // for void types, these are common to all the
williamr@2: // implementation above:
williamr@2: //
williamr@2: #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
williamr@2: #   define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
williamr@2:     BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2,value) \
williamr@2:     BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const,value) \
williamr@2:     BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 volatile,value) \
williamr@2:     BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const volatile,value) \
williamr@2:     /**/
williamr@2: 
williamr@2: #   define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(trait,spec1,spec2,value) \
williamr@2:     TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
williamr@2:     TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const,spec2,value) \
williamr@2:     TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 volatile,spec2,value) \
williamr@2:     TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const volatile,spec2,value) \
williamr@2:     /**/
williamr@2: 
williamr@2:     TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(is_convertible,void,void,true)
williamr@2: 
williamr@2: #   undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2
williamr@2: #   undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1
williamr@2: 
williamr@2: #else
williamr@2:     BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(is_convertible,void,void,true)
williamr@2: #endif // BOOST_NO_CV_VOID_SPECIALIZATIONS
williamr@2: 
williamr@2: #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void,To,false)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void,true)
williamr@2: #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const,To,false)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void volatile,To,false)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const volatile,To,false)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const,true)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void volatile,true)
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const volatile,true)
williamr@2: #endif
williamr@2: #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
williamr@2: 
williamr@2: } // namespace detail
williamr@2: 
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_convertible,From,To,(::boost::detail::is_convertible_impl_dispatch<From,To>::value))
williamr@2: 
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #include <boost/type_traits/detail/bool_trait_undef.hpp>
williamr@2: 
williamr@2: #endif // BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
williamr@2: