casts.hpp

来自「CGAL is a collaborative effort of severa」· HPP 代码 · 共 220 行

// - casts.hpp -- BLambda Library -------------
//
// 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 http://www.boost.org

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

#if !defined(BOOST_LAMBDA_CASTS_HPP)
#define BOOST_LAMBDA_CASTS_HPP

#include <typeinfo>

namespace boost { 
namespace lambda {

template<class T> class cast_action;

template<class T> class static_cast_action;
template<class T> class dynamic_cast_action;
template<class T> class const_cast_action;
template<class T> class reinterpret_cast_action;

class typeid_action;
class sizeof_action;

// Cast actions

template<class T> class cast_action<static_cast_action<T> > 
{
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return static_cast<RET>(a1);
  }
};

template<class T> class cast_action<dynamic_cast_action<T> > {
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return dynamic_cast<RET>(a1);
  }
};

template<class T> class cast_action<const_cast_action<T> > {
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return const_cast<RET>(a1);
  }
};

template<class T> class cast_action<reinterpret_cast_action<T> > {
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return reinterpret_cast<RET>(a1);
  }
};

  // typedid action
class typeid_action {
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return typeid(a1);
  }
};

// sizeof action
class sizeof_action
{
public:
  template<class RET, class Arg1>
  static RET apply(Arg1 &a1) {
    return sizeof(a1);
  }
};


// return types of casting lambda_functors (all "T" type.)

template<template <class> class cast_type, class T, class A>
struct return_type_N<cast_action< cast_type<T> >, A> { 
  typedef T type;
};

// return type of typeid_action
template<class A>
struct return_type_N<typeid_action, A> { 
  typedef std::type_info const & type;
};

// return type of sizeof_action

template<class A>
struct return_type_N<sizeof_action, A> { 
  typedef std::size_t type;
};


// the four cast & typeid overloads.
// casts can take ordinary variables (not just lambda functors)

// static_cast 
template <class T, class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, cast_action<static_cast_action<T> > >, 
    tuple<typename const_copy_argument <const Arg1>::type>
  > 
>
ll_static_cast(const Arg1& a1) { 
  return 
    lambda_functor_base<
      action<1, cast_action<static_cast_action<T> > >, 
      tuple<typename const_copy_argument <const Arg1>::type> 
    >
  ( tuple<typename const_copy_argument <const Arg1>::type>(a1));
}

// dynamic_cast
template <class T, class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, cast_action<dynamic_cast_action<T> > >, 
    tuple<typename const_copy_argument <const Arg1>::type>
  > 
>
ll_dynamic_cast(const Arg1& a1) { 
  return 
    lambda_functor_base<
      action<1, cast_action<dynamic_cast_action<T> > >, 
      tuple<typename const_copy_argument <const Arg1>::type>
    > 
  ( tuple<typename const_copy_argument <const Arg1>::type>(a1));
}

// const_cast
template <class T, class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, cast_action<const_cast_action<T> > >, 
    tuple<typename const_copy_argument <const Arg1>::type>
  > 
>
ll_const_cast(const Arg1& a1) { 
  return 
      lambda_functor_base<
        action<1, cast_action<const_cast_action<T> > >, 
        tuple<typename const_copy_argument <const Arg1>::type>
      > 
      ( tuple<typename const_copy_argument <const Arg1>::type>(a1));
}

// reinterpret_cast
template <class T, class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, cast_action<reinterpret_cast_action<T> > >, 
    tuple<typename const_copy_argument <const Arg1>::type>
  > 
>
ll_reinterpret_cast(const Arg1& a1) { 
  return 
      lambda_functor_base<
        action<1, cast_action<reinterpret_cast_action<T> > >, 
        tuple<typename const_copy_argument <const Arg1>::type> 
      > 
      ( tuple<typename const_copy_argument <const Arg1>::type>(a1));
}

// typeid
// can be applied to a normal variable as well (can refer to a polymorphic
// class object)
template <class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, typeid_action>, 
    tuple<typename const_copy_argument <const Arg1>::type>
  > 
>
ll_typeid(const Arg1& a1) { 
  return 
      lambda_functor_base<
        action<1, typeid_action>, 
        tuple<typename const_copy_argument <const Arg1>::type>
      > 
      ( tuple<typename const_copy_argument <const Arg1>::type>(a1));
}

// sizeof(expression)
// Always takes a lambda expression (if not, built in sizeof will do)
template <class Arg1>
inline const lambda_functor<
  lambda_functor_base<
    action<1, sizeof_action>, 
    tuple<lambda_functor<Arg1> >
  > 
>
ll_sizeof(const lambda_functor<Arg1>& a1) { 
  return 
      lambda_functor_base<
        action<1, sizeof_action>, 
        tuple<lambda_functor<Arg1> >
      > 
      ( tuple<lambda_functor<Arg1> >(a1));
}

} // namespace lambda 
} // namespace boost

#endif