Chris@102: // Boost enable_if library
Chris@102: 
Chris@102: // Copyright 2003 (c) The Trustees of Indiana University.
Chris@102: 
Chris@102: // Use, modification, and distribution is subject to the Boost Software
Chris@102: // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@102: // http://www.boost.org/LICENSE_1_0.txt)
Chris@102: 
Chris@102: //    Authors: Jaakko Jarvi (jajarvi at osl.iu.edu)
Chris@102: //             Jeremiah Willcock (jewillco at osl.iu.edu)
Chris@102: //             Andrew Lumsdaine (lums at osl.iu.edu)
Chris@102: 
Chris@102: 
Chris@102: #ifndef BOOST_CORE_ENABLE_IF_HPP
Chris@102: #define BOOST_CORE_ENABLE_IF_HPP
Chris@102: 
Chris@102: #include "boost/config.hpp"
Chris@102: 
Chris@102: // Even the definition of enable_if causes problems on some compilers,
Chris@102: // so it's macroed out for all compilers that do not support SFINAE
Chris@102: 
Chris@102: #ifndef BOOST_NO_SFINAE
Chris@102: 
Chris@102: namespace boost
Chris@102: {
Chris@102:  
Chris@102:   template <bool B, class T = void>
Chris@102:   struct enable_if_c {
Chris@102:     typedef T type;
Chris@102:   };
Chris@102: 
Chris@102:   template <class T>
Chris@102:   struct enable_if_c<false, T> {};
Chris@102: 
Chris@102:   template <class Cond, class T = void> 
Chris@102:   struct enable_if : public enable_if_c<Cond::value, T> {};
Chris@102: 
Chris@102:   template <bool B, class T>
Chris@102:   struct lazy_enable_if_c {
Chris@102:     typedef typename T::type type;
Chris@102:   };
Chris@102: 
Chris@102:   template <class T>
Chris@102:   struct lazy_enable_if_c<false, T> {};
Chris@102: 
Chris@102:   template <class Cond, class T> 
Chris@102:   struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};
Chris@102: 
Chris@102: 
Chris@102:   template <bool B, class T = void>
Chris@102:   struct disable_if_c {
Chris@102:     typedef T type;
Chris@102:   };
Chris@102: 
Chris@102:   template <class T>
Chris@102:   struct disable_if_c<true, T> {};
Chris@102: 
Chris@102:   template <class Cond, class T = void> 
Chris@102:   struct disable_if : public disable_if_c<Cond::value, T> {};
Chris@102: 
Chris@102:   template <bool B, class T>
Chris@102:   struct lazy_disable_if_c {
Chris@102:     typedef typename T::type type;
Chris@102:   };
Chris@102: 
Chris@102:   template <class T>
Chris@102:   struct lazy_disable_if_c<true, T> {};
Chris@102: 
Chris@102:   template <class Cond, class T> 
Chris@102:   struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};
Chris@102: 
Chris@102: } // namespace boost
Chris@102: 
Chris@102: #else
Chris@102: 
Chris@102: namespace boost {
Chris@102: 
Chris@102:   namespace detail { typedef void enable_if_default_T; }
Chris@102: 
Chris@102:   template <typename T>
Chris@102:   struct enable_if_does_not_work_on_this_compiler;
Chris@102: 
Chris@102:   template <bool B, class T = detail::enable_if_default_T>
Chris@102:   struct enable_if_c : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <bool B, class T = detail::enable_if_default_T> 
Chris@102:   struct disable_if_c : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <bool B, class T = detail::enable_if_default_T> 
Chris@102:   struct lazy_enable_if_c : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <bool B, class T = detail::enable_if_default_T> 
Chris@102:   struct lazy_disable_if_c : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <class Cond, class T = detail::enable_if_default_T> 
Chris@102:   struct enable_if : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <class Cond, class T = detail::enable_if_default_T> 
Chris@102:   struct disable_if : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <class Cond, class T = detail::enable_if_default_T> 
Chris@102:   struct lazy_enable_if : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102:   template <class Cond, class T = detail::enable_if_default_T> 
Chris@102:   struct lazy_disable_if : enable_if_does_not_work_on_this_compiler<T>
Chris@102:   { };
Chris@102: 
Chris@102: } // namespace boost
Chris@102: 
Chris@102: #endif // BOOST_NO_SFINAE
Chris@102: 
Chris@102: #endif