ceph/src/boost/libs/phoenix/example/factorial.cpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2003 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #include <vector>
   8 #include <algorithm>
   9 #include <iostream>
  10 #include <boost/phoenix/core.hpp>
  11 #include <boost/phoenix/function.hpp>
  12
  13 struct factorial_impl
  14 {
  15     template <typename Sig>
  16     struct result;
  17
  18     template <typename This, typename Arg>
  19     struct result<This(Arg)>
  20         : result<This(Arg const &)>
  21     {};
  22
  23     template <typename This, typename Arg>
  24     struct result<This(Arg &)>
  25     {
  26         typedef Arg type;
  27     };
  28
  29     template <typename Arg>
  30     Arg operator()(Arg n) const
  31     {
  32         return (n <= 0) ? 1 : n * this->operator()(n-1);
  33     }
  34 };
  35
  36
  37 int
  38 main()
  39 {
  40     using boost::phoenix::arg_names::arg1;
  41     boost::phoenix::function<factorial_impl> factorial;
  42     int i = 4;
  43     std::cout << factorial(i)() << std::endl;
  44     std::cout << factorial(arg1)(i) << std::endl;
  45     return 0;
  46 }