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

   1 /*=============================================================================
   2     Copyright (c) 2001-2007 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
   8 #include <boost/phoenix.hpp>
   9
  10 #include <iostream>
  11 #include <sstream>
  12
  13 namespace proto = boost::proto;
  14 namespace phoenix = boost::phoenix;
  15
  16 template <typename Rule>
  17 struct identity_transform;
  18
  19 struct identity_actions
  20 {
  21     template <typename Rule>
  22     struct when : phoenix::call<identity_transform<Rule> > {};
  23 };
  24
  25 template <>
  26 struct identity_actions::when<phoenix::rule::argument>
  27     : proto::call<
  28         identity_transform<phoenix::rule::argument>(proto::_value, phoenix::_context)
  29     > {};
  30
  31 template <>
  32 struct identity_actions::when<phoenix::rule::terminal>
  33     : proto::call<
  34         identity_transform<phoenix::rule::terminal>(proto::_value, phoenix::_context)
  35     > {};
  36
  37 template <>
  38 struct identity_actions::when<phoenix::rule::custom_terminal>
  39     : proto::lazy<
  40         identity_transform<proto::_value>(proto::_value, phoenix::_context)
  41     > {};
  42
  43 template <>
  44 struct identity_transform<phoenix::rule::terminal>
  45 {
  46     typedef std::string result_type;
  47
  48     template <typename Terminal, typename Context>
  49     std::string operator()(Terminal const & terminal, Context) const
  50     {
  51         std::stringstream ss;
  52         ss << "val(" << terminal << ")";
  53         return ss.str();
  54     }
  55
  56     template <typename Context>
  57     std::string operator()(char const * terminal, Context) const
  58     {
  59         std::stringstream ss;
  60         ss << "val(\"" << terminal << "\")";
  61         return ss.str();
  62     }
  63 };
  64
  65 template <typename T>
  66 struct identity_transform<boost::reference_wrapper<T> >
  67 {
  68     typedef std::string result_type;
  69
  70     template <typename Terminal, typename Context>
  71     std::string operator()(Terminal const & terminal, Context) const
  72     {
  73         std::stringstream ss;
  74         ss << "ref(" << terminal << ")";
  75         return ss.str();
  76     }
  77
  78
  79     template <int N, typename Context>
  80     std::string operator()(boost::reference_wrapper<char const *> terminal, Context) const
  81     {
  82         std::stringstream ss;
  83         ss << "ref(\"" << terminal << "\")";
  84         return ss.str();
  85     }
  86
  87     template <int N, typename Context>
  88     std::string operator()(boost::reference_wrapper<char const [N]> terminal, Context) const
  89     {
  90         std::stringstream ss;
  91         ss << "ref(\"" << terminal << "\")";
  92         return ss.str();
  93     }
  94 };
  95
  96 template <>
  97 struct identity_transform<phoenix::rule::argument>
  98 {
  99     typedef std::string result_type;
 100
 101     template <typename N, typename Context>
 102     std::string operator()(N, Context) const
 103     {
 104         std::stringstream ss;
 105         ss << "_" << N::value;
 106         return ss.str();
 107     }
 108 };
 109
 110
 111 template <typename Expr>
 112 void identity(Expr const & expr)
 113 {
 114     std::cout << phoenix::eval(expr, phoenix::context(int(), identity_actions())) << "\n";
 115 }
 116
 117 int main()
 118 {
 119
 120     identity(phoenix::val(8));
 121     identity(phoenix::val("8"));
 122     identity(phoenix::ref("blubb"));
 123     identity(phoenix::arg_names::_1);
 124 }