switch.hpp

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// Boost Lambda Library -- switch.hpp -----------------------------------
//
// Copyright (C) 2000 Gary Powell ([e-mail])
// Copyright (C) 1999, 2000 Jaakko J鋜vi ([e-mail])
//
// Distributed under 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)
//
// For more information, see www.boost.org

// --------------------------------------------------------------------------

#if !defined(BOOST_LAMBDA_SWITCH_HPP)
#define BOOST_LAMBDA_SWITCH_HPP

#include "boost/lambda/core.hpp"
#include "boost/lambda/detail/control_constructs_common.hpp"

#include "boost/preprocessor/enum_shifted_params.hpp"
#include "boost/preprocessor/repeat_2nd.hpp"
#include "boost/preprocessor/tuple.hpp"

namespace boost { 
namespace lambda {

// Switch actions
template <int N, class Switch1 = null_type, class Switch2 = null_type, 
          class Switch3 = null_type, class Switch4 = null_type,
          class Switch5 = null_type, class Switch6 = null_type, 
          class Switch7 = null_type, class Switch8 = null_type, 
          class Switch9 = null_type>
struct switch_action {};


namespace detail {

  // templates to represent special lambda functors for the cases in 
  // switch statements
  
template <int Value> struct case_label {};
struct default_label {};

template<class Type> struct switch_case_tag {};

  // a normal case is represented as:
  // tagged_lambda_functor<switch_case_tag<case_label<N> > >, LambdaFunctor>
  
  // the default case as:
  // tagged_lambda_functor<switch_case_tag<default_label> >, LambdaFunctor>


} // end detail


/// create switch_case_tag tagged_lambda_functors
template <int CaseValue, class Arg>
inline const 
tagged_lambda_functor<
  detail::switch_case_tag<detail::case_label<CaseValue> >, 
  lambda_functor<Arg> 
> 
case_statement(const lambda_functor<Arg>& a) { 
  return 
    tagged_lambda_functor<
      detail::switch_case_tag<detail::case_label<CaseValue> >, 
      lambda_functor<Arg> 
    >(a); 
}

// No case body case.
template <int CaseValue>
inline const 
tagged_lambda_functor<
  detail::switch_case_tag<detail::case_label<CaseValue> >,
  lambda_functor< 
    lambda_functor_base< 
      do_nothing_action, 
      null_type
    > 
  > 
> 
case_statement() { 
return 
  tagged_lambda_functor<
    detail::switch_case_tag<detail::case_label<CaseValue> >,
    lambda_functor< 
      lambda_functor_base< 
        do_nothing_action, 
        null_type
      > 
    > 
  > () ;
}

// default label
template <class Arg>
inline const 
tagged_lambda_functor<
  detail::switch_case_tag<detail::default_label>, 
  lambda_functor<Arg> 
> 
default_statement(const lambda_functor<Arg>& a) { 
  return 
    tagged_lambda_functor<
      detail::switch_case_tag<detail::default_label>, 
      lambda_functor<Arg> 
    >(a); 
}

// default lable, no case body case.
inline const 
tagged_lambda_functor<
  detail::switch_case_tag<detail::default_label>,
  lambda_functor< 
    lambda_functor_base< 
      do_nothing_action, 
      null_type
    > 
  > 
> 
default_statement() { 
return 
      lambda_functor_base< 
        do_nothing_action, 
        null_type 
      > () ;
}


// Specializations for lambda_functor_base of case_statement -----------------

// 0 case type:
// useless (just the condition part) but provided for completeness.
template<class Args>
class 
lambda_functor_base<
  switch_action<1>, 
  Args
> 
{
public:
  Args args;
  template <class SigArgs> struct sig { typedef void type; };
public:
  explicit lambda_functor_base(const Args& a) : args(a) {}

  template<class RET, CALL_TEMPLATE_ARGS>
  RET call(CALL_FORMAL_ARGS) const {
    detail::select(::boost::tuples::get<1>(args), CALL_ACTUAL_ARGS);  
  }
};

// 1 case type:
// template<class Args, int Case1>
// class 
// lambda_functor_base<
//   action<
//     2, 
//     return_void_action<switch_action<detail::case_label<Case1> > > 
//   >, 
//   Args
// > 
// {
//   Args args;
// public:
//   explicit lambda_functor_base(const Args& a) : args(a) {}

//   template<class RET, class A, class B, class C>
//   RET call(A& a, B& b, C& c) const {
//     switch( detail::select(::boost::tuples::get<0>(args), a, b, c) )  
//     {
//       case Case1:                
//         detail::select(::boost::tuples::get<1>(args), a, b, c);
//         break;
//     }
//   }
// };

// switch with default being the sole label - doesn't make much sense but
// it is there for completeness
// template<class Args>
// class
// lambda_functor_base<
//   action<
//     2,
//     return_void_action<switch_action<detail::default_label> >
//   >,
//   Args
// >
// {
//   Args args;
// public:
//   explicit lambda_functor_base(const Args& a) : args(a) {}
// 
//   template<class RET, class A, class B, class C>
//   RET call(A& a, B& b, C& c) const {
//     switch( detail::select(::boost::tuples::get<0>(args), a, b, c) )
//     {
//       default:
//         detail::select(::boost::tuples::get<1>(args), a, b, c);
//         break;
//     }
//   }
// };



// // 2 case type:
// The different specializations are generated with Vesa Karvonen's 
// preprocessor library.

// This is just a comment to show what the generated classes look like

// template<class Args, int Case1, int Case2>
// class 
// lambda_functor_base<
//   action<3, 
//     return_void_action< 
//       switch_action< 
//         detail::case_label<Case1>,
//         detail::case_label<Case2>
//       > 
//     > 
//   >, 
//   Args
// > 
// {
//   Args args;
// public:
//   explicit lambda_functor_base(const Args& a) : args(a) {}

//   template<class RET, class A, class B, class C>
//   RET call(A& a, B& b, C& c) const {
//     switch( detail::select(::boost::tuples::get<0>(args), a, b, c) )  
//     {
//       case Case1:                
//         detail::select(::boost::tuples::get<1>(args), a, b, c);
//         break;
//       case Case2:                
//         detail::select(::boost::tuples::get<2>(args), a, b, c);
//         break;
//     }
//   }
// };

// template<class Args, int Case1>
// class 
// lambda_functor_base<
//   action<3, 
//     return_void_action< 
//       switch_action<