forked from boostorg/mpl
160 lines
3.4 KiB
C++
160 lines
3.4 KiB
C++
//-----------------------------------------------------------------------------
|
|
// boost/mpl/if.hpp header file
|
|
// See http://www.boost.org for updates, documentation, and revision history.
|
|
//-----------------------------------------------------------------------------
|
|
//
|
|
// Copyright (c) 2000-02 Boost.org
|
|
//
|
|
// Permission to use, copy, modify, distribute and sell this software
|
|
// and its documentation for any purpose is hereby granted without fee,
|
|
// provided that the above copyright notice appears in all copies and
|
|
// that both the copyright notice and this permission notice appear in
|
|
// supporting documentation. No representations are made about the
|
|
// suitability of this software for any purpose. It is provided "as is"
|
|
// without express or implied warranty.
|
|
|
|
#ifndef BOOST_MPL_IF_HPP_INCLUDED
|
|
#define BOOST_MPL_IF_HPP_INCLUDED
|
|
|
|
#include "boost/mpl/aux_/value_wknd.hpp"
|
|
#include "boost/mpl/aux_/void_spec.hpp"
|
|
#include "boost/mpl/aux_/lambda_support.hpp"
|
|
#include "boost/config.hpp"
|
|
|
|
namespace boost {
|
|
namespace mpl {
|
|
|
|
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
|
|
|
|
template<
|
|
bool C
|
|
, typename T1
|
|
, typename T2
|
|
>
|
|
struct if_c
|
|
{
|
|
typedef T1 type;
|
|
};
|
|
|
|
template<
|
|
typename T1
|
|
, typename T2
|
|
>
|
|
struct if_c<false,T1,T2>
|
|
{
|
|
typedef T2 type;
|
|
};
|
|
|
|
template<
|
|
typename BOOST_MPL_AUX_VOID_SPEC_PARAM(C)
|
|
, typename BOOST_MPL_AUX_VOID_SPEC_PARAM(T1)
|
|
, typename BOOST_MPL_AUX_VOID_SPEC_PARAM(T2)
|
|
>
|
|
struct if_
|
|
{
|
|
typedef typename if_c<
|
|
BOOST_MPL_AUX_VALUE_WKND(C)::value
|
|
, T1
|
|
, T2
|
|
>::type type;
|
|
|
|
BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(C,T1,T2))
|
|
};
|
|
|
|
#elif defined(BOOST_MSVC) && (BOOST_MSVC <= 1200)
|
|
|
|
// MSVC6.5-specific version
|
|
|
|
template<
|
|
bool C
|
|
, typename T1
|
|
, typename T2
|
|
>
|
|
struct if_c
|
|
{
|
|
private:
|
|
template<bool> struct answer { typedef T1 type; };
|
|
template<> struct answer<false> { typedef T2 type; };
|
|
|
|
public:
|
|
typedef typename answer< C >::type type;
|
|
};
|
|
|
|
// (almost) copy & paste in order to save one more
|
|
// recursively nested template instantiation to user
|
|
template<
|
|
typename C
|
|
, typename T1
|
|
, typename T2
|
|
>
|
|
struct if_
|
|
{
|
|
private:
|
|
template<bool> struct answer { typedef T1 type; };
|
|
template<> struct answer<false> { typedef T2 type; };
|
|
|
|
public:
|
|
typedef typename answer< C::value >::type type;
|
|
};
|
|
|
|
#else
|
|
|
|
// no partial class template specialization
|
|
|
|
namespace aux {
|
|
|
|
template< bool C >
|
|
struct if_impl
|
|
{
|
|
template< typename T1, typename T2 > struct result_
|
|
{
|
|
typedef T1 type;
|
|
};
|
|
};
|
|
|
|
template<>
|
|
struct if_impl<false>
|
|
{
|
|
template< typename T1, typename T2 > struct result_
|
|
{
|
|
typedef T2 type;
|
|
};
|
|
};
|
|
|
|
} // namespace aux
|
|
|
|
template<
|
|
bool C
|
|
, typename T1
|
|
, typename T2
|
|
>
|
|
struct if_c
|
|
{
|
|
typedef typename aux::if_impl< C >
|
|
::template result_<T1,T2>::type type;
|
|
};
|
|
|
|
// (almost) copy & paste in order to save one more
|
|
// recursively nested template instantiation to user
|
|
template<
|
|
typename BOOST_MPL_AUX_VOID_SPEC_PARAM(C)
|
|
, typename BOOST_MPL_AUX_VOID_SPEC_PARAM(T1)
|
|
, typename BOOST_MPL_AUX_VOID_SPEC_PARAM(T2)
|
|
>
|
|
struct if_
|
|
{
|
|
typedef typename aux::if_impl< C::value >
|
|
::template result_<T1,T2>::type type;
|
|
|
|
BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(C,T1,T2))
|
|
};
|
|
|
|
#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
|
|
|
|
BOOST_MPL_AUX_VOID_SPEC(3, if_)
|
|
|
|
} // namespace mpl
|
|
} // namespace boost
|
|
|
|
#endif // BOOST_MPL_IF_HPP_INCLUDED
|