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Constexpr conversion to MPL types #134

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Constexpr conversion to MPL types #134

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16 changes: 4 additions & 12 deletions include/boost/type_traits/integral_constant.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -57,12 +57,8 @@ namespace boost{
typedef integral_constant<T, val> type;
static const T value = val;

operator const mpl::integral_c<T, val>& ()const
{
static const char data[sizeof(long)] = { 0 };
static const void* pdata = data;
return *(reinterpret_cast<const mpl::integral_c<T, val>*>(pdata));
}
BOOST_CONSTEXPR operator mpl::integral_c<T, val>()const
{ return mpl::integral_c<T, val>(); }
BOOST_CONSTEXPR operator T()const { return val; }
};

Expand All @@ -77,12 +73,8 @@ namespace boost{
typedef integral_constant<bool, val> type;
static const bool value = val;

operator const mpl::bool_<val>& ()const
{
static const char data[sizeof(long)] = { 0 };
static const void* pdata = data;
return *(reinterpret_cast<const mpl::bool_<val>*>(pdata));
}
BOOST_CONSTEXPR operator mpl::bool_<val>()const
{ return mpl::bool_<val>(); }
BOOST_CONSTEXPR operator bool()const { return val; }
};

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25 changes: 20 additions & 5 deletions test/mpl_interop_test1.cpp
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Expand Up @@ -5,26 +5,41 @@
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#include <boost/type_traits/is_void.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/config.hpp>

template <class T>
int dispatch_test_imp(const boost::mpl::bool_<true>&)
BOOST_CONSTEXPR int dispatch_test_imp1(const boost::mpl::bool_<true>&)
{
return 0;
}
template <class T>
int dispatch_test_imp(const boost::mpl::bool_<false>&)
BOOST_CONSTEXPR int dispatch_test_imp1(const boost::mpl::bool_<false>&)
{
return 1;
}

template <class T>
int dispatch_test()
BOOST_CONSTEXPR int dispatch_test_imp2(boost::mpl::true_)
{
return dispatch_test_imp<T>(boost::is_void<T>());
return 0;
}
template <class T>
BOOST_CONSTEXPR int dispatch_test_imp2(boost::mpl::false_)
{
return 1;
}

template <class T>
BOOST_CONSTEXPR int dispatch_test()
{
return dispatch_test_imp1<T>(boost::is_void<T>()) +
dispatch_test_imp2<T>(boost::is_void<T>());
}


int main()
{
return (dispatch_test<int>() == 1) && (dispatch_test<void>() == 0) ? 0 : 1;
BOOST_CONSTEXPR bool result = (dispatch_test<int>() == 2) && (dispatch_test<void>() == 0);
return result ? 0 : 1;
}