// 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