text: // Boost enable_if library
  
  // Copyright 2003 (c) 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 Jarvi (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
  