// Boost enable_if library

// Copyright 2003 © The Trustees of Indiana University.

// Use, modification, and distribution is 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)

//    Authors: Jaakko Järvi (jajarvi at osl.iu.edu)

//             Jeremiah Willcock (jewillco at osl.iu.edu)

//             Andrew Lumsdaine (lums at osl.iu.edu)

#ifndef BOOST_UTILITY_ENABLE_IF_HPP

#define BOOST_UTILITY_ENABLE_IF_HPP

#include "boost/config.hpp"

// Even the definition of enable_if causes problems on some compilers,

// so it's macroed out for all compilers that do not support SFINAE

#ifndef BOOST_NO_SFINAE

namespace boost

{

  template <bool B, class T = void>

  struct enable_if_c {

    typedef T type;

  };

  template <class T>

  struct enable_if_c<false, T> {};

  template <class Cond, class T = void> 

  struct enable_if : public enable_if_c<Cond::value, T> {};

  template <bool B, class T>

  struct lazy_enable_if_c {

    typedef typename T::type type;

  };

  template <class T>

  struct lazy_enable_if_c<false, T> {};

  template <class Cond, class T> 

  struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};

  template <bool B, class T = void>

  struct disable_if_c {

    typedef T type;

  };

  template <class T>

  struct disable_if_c<true, T> {};

  template <class Cond, class T = void> 

  struct disable_if : public disable_if_c<Cond::value, T> {};

  template <bool B, class T>

  struct lazy_disable_if_c {

    typedef typename T::type type;

  };

  template <class T>

  struct lazy_disable_if_c<true, T> {};

  template <class Cond, class T> 

  struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};

} // namespace boost

#else

namespace boost {

  namespace detail { typedef void enable_if_default_T; }

  template <typename T>

  struct enable_if_does_not_work_on_this_compiler;

  template <bool B, class T = detail::enable_if_default_T>

  struct enable_if_c : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <bool B, class T = detail::enable_if_default_T> 

  struct disable_if_c : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <bool B, class T = detail::enable_if_default_T> 

  struct lazy_enable_if_c : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <bool B, class T = detail::enable_if_default_T> 

  struct lazy_disable_if_c : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <class Cond, class T = detail::enable_if_default_T> 

  struct enable_if : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <class Cond, class T = detail::enable_if_default_T> 

  struct disable_if : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <class Cond, class T = detail::enable_if_default_T> 

  struct lazy_enable_if : enable_if_does_not_work_on_this_compiler<T>

  { };

  template <class Cond, class T = detail::enable_if_default_T> 

  struct lazy_disable_if : enable_if_does_not_work_on_this_compiler<T>

  { };

} // namespace boost

#endif // BOOST_NO_SFINAE

#endif