boost/type_traits/is_empty.hpp
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt).
//
// See http://www.boost.org/libs/type_traits for most recent version including documentation.
#ifndef BOOST_TT_IS_EMPTY_HPP_INCLUDED
#define BOOST_TT_IS_EMPTY_HPP_INCLUDED
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/detail/ice_or.hpp>
#include <boost/type_traits/config.hpp>
#include <boost/type_traits/intrinsics.hpp>
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
# include <boost/type_traits/remove_cv.hpp>
# include <boost/type_traits/is_class.hpp>
# include <boost/type_traits/add_reference.hpp>
#else
# include <boost/type_traits/is_reference.hpp>
# include <boost/type_traits/is_pointer.hpp>
# include <boost/type_traits/is_member_pointer.hpp>
# include <boost/type_traits/is_array.hpp>
# include <boost/type_traits/is_void.hpp>
# include <boost/type_traits/detail/ice_and.hpp>
# include <boost/type_traits/detail/ice_not.hpp>
#endif
// should be always the last #include directive
#include <boost/type_traits/detail/bool_trait_def.hpp>
namespace boost {
namespace detail {
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
template <typename T>
struct empty_helper_t1 : public T
{
empty_helper_t1(); // hh compiler bug workaround
int i[256];
private:
// suppress compiler warnings:
empty_helper_t1(const empty_helper_t1&);
empty_helper_t1& operator=(const empty_helper_t1&);
};
struct empty_helper_t2 { int i[256]; };
#if !BOOST_WORKAROUND(__BORLANDC__, < 0x600)
template <typename T, bool is_a_class = false>
struct empty_helper
{
BOOST_STATIC_CONSTANT(bool, value = false);
};
template <typename T>
struct empty_helper<T, true>
{
BOOST_STATIC_CONSTANT(
bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2))
);
};
template <typename T>
struct is_empty_impl
{
typedef typename remove_cv<T>::type cvt;
BOOST_STATIC_CONSTANT(
bool, value = (
::boost::type_traits::ice_or<
::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value
, BOOST_IS_EMPTY(cvt)
>::value
));
};
#else // __BORLANDC__
template <typename T, bool is_a_class, bool convertible_to_int>
struct empty_helper
{
BOOST_STATIC_CONSTANT(bool, value = false);
};
template <typename T>
struct empty_helper<T, true, false>
{
BOOST_STATIC_CONSTANT(bool, value = (
sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)
));
};
template <typename T>
struct is_empty_impl
{
typedef typename remove_cv<T>::type cvt;
typedef typename add_reference<T>::type r_type;
BOOST_STATIC_CONSTANT(
bool, value = (
::boost::type_traits::ice_or<
::boost::detail::empty_helper<
cvt
, ::boost::is_class<T>::value
, ::boost::is_convertible< r_type,int>::value
>::value
, BOOST_IS_EMPTY(cvt)
>::value));
};
#endif // __BORLANDC__
#else // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
#ifdef BOOST_MSVC6_MEMBER_TEMPLATES
template <typename T>
struct empty_helper_t1 : public T
{
empty_helper_t1();
int i[256];
};
struct empty_helper_t2 { int i[256]; };
template <typename T>
struct empty_helper_base
{
enum { value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) };
};
template <typename T>
struct empty_helper_nonbase
{
enum { value = false };
};
template <bool base>
struct empty_helper_chooser
{
template <typename T> struct result_
{
typedef empty_helper_nonbase<T> type;
};
};
template <>
struct empty_helper_chooser<true>
{
template <typename T> struct result_
{
typedef empty_helper_base<T> type;
};
};
template <typename T>
struct is_empty_impl
{
typedef ::boost::detail::empty_helper_chooser<
::boost::type_traits::ice_and<
::boost::type_traits::ice_not< ::boost::is_reference<T>::value >::value,
::boost::type_traits::ice_not< ::boost::is_convertible<T,double>::value >::value,
::boost::type_traits::ice_not< ::boost::is_pointer<T>::value >::value,
::boost::type_traits::ice_not< ::boost::is_member_pointer<T>::value >::value,
::boost::type_traits::ice_not< ::boost::is_array<T>::value >::value,
::boost::type_traits::ice_not< ::boost::is_void<T>::value >::value,
::boost::type_traits::ice_not<
::boost::is_convertible<T,void const volatile*>::value
>::value
>::value > chooser;
typedef typename chooser::template result_<T> result;
typedef typename result::type eh_type;
BOOST_STATIC_CONSTANT(bool, value =
(::boost::type_traits::ice_or<eh_type::value, BOOST_IS_EMPTY(T)>::value));
};
#else
template <typename T> struct is_empty_impl
{
BOOST_STATIC_CONSTANT(bool, value = BOOST_IS_EMPTY(T));
};
#endif // BOOST_MSVC6_MEMBER_TEMPLATES
#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
// these help when the compiler has no partial specialization support:
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void,false)
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void volatile,false)
BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const volatile,false)
#endif
} // namespace detail
BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_empty,T,::boost::detail::is_empty_impl<T>::value)
} // namespace boost
#include <boost/type_traits/detail/bool_trait_undef.hpp>
#endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED