// 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