// 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

