Boost C++ Libraries

boost/smart_ptr/detail/sp_convertible.hpp

#ifndef BOOST_SMART_PTR_DETAIL_SP_CONVERTIBLE_HPP_INCLUDED
#define BOOST_SMART_PTR_DETAIL_SP_CONVERTIBLE_HPP_INCLUDED

// MS compatible compilers support #pragma once

#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

//  detail/sp_convertible.hpp
//
//  Copyright 2008 Peter Dimov
//
//  Distributed under 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

#include <boost/config.hpp>
#include <cstddef>

namespace boost
{

namespace detail
{

template< class Y, class T > struct sp_convertible
{
    typedef char (&yes) [1];
    typedef char (&no)  [2];

    static yes f( T* );
    static no  f( ... );

    enum _vt { value = sizeof( (f)( static_cast<Y*>(0) ) ) == sizeof(yes) };
};

template< class Y, class T > struct sp_convertible< Y, T[] >
{
    enum _vt { value = false };
};

template< class Y, class T > struct sp_convertible< Y[], T[] >
{
    enum _vt { value = sp_convertible< Y[1], T[1] >::value };
};

template< class Y, std::size_t N, class T > struct sp_convertible< Y[N], T[] >
{
    enum _vt { value = sp_convertible< Y[1], T[1] >::value };
};

struct sp_empty
{
};

template< bool > struct sp_enable_if_convertible_impl;

template<> struct sp_enable_if_convertible_impl<true>
{
    typedef sp_empty type;
};

template<> struct sp_enable_if_convertible_impl<false>
{
};

template< class Y, class T > struct sp_enable_if_convertible: public sp_enable_if_convertible_impl< sp_convertible< Y, T >::value >
{
};

} // namespace detail

} // namespace boost

#endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_CONVERTIBLE_HPP_INCLUDED