    // 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 DLIB_BOOST_UTILITY_ENABLE_IF_HPP
    #define DLIB_BOOST_UTILITY_ENABLE_IF_HPP

    namespace dlib
    {

      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 dlib

    #endif // DLIB_BOOST_UTILITY_ENABLE_IF_HPP