// Boost Lambda Library -  lambda_functors.hpp -------------------------------

// Copyright (C) 1999, 2000 Jaakko Järvi (jaakko.jarvi@cs.utu.fi)

//

// 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

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

#ifndef BOOST_LAMBDA_LAMBDA_FUNCTORS_HPP

#define BOOST_LAMBDA_LAMBDA_FUNCTORS_HPP

namespace boost { 

namespace lambda {

// -- lambda_functor --------------------------------------------

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

//inline const null_type const_null_type() { return null_type(); }

namespace detail {

namespace {

  static const null_type constant_null_type = null_type();

} // unnamed

} // detail

class unused {};

#define cnull_type() detail::constant_null_type

// -- free variables types -------------------------------------------------- 

  // helper to work around the case where the nullary return type deduction 

  // is always performed, even though the functor is not nullary  

namespace detail {

  template<int N, class Tuple> struct get_element_or_null_type {

    typedef typename 

      detail::tuple_element_as_reference<N, Tuple>::type type;

  };

  template<int N> struct get_element_or_null_type<N, null_type> {

    typedef null_type type;

  };

}

template <int I> struct placeholder;

template<> struct placeholder<FIRST> {

  template<class SigArgs> struct sig {

    typedef typename detail::get_element_or_null_type<0, SigArgs>::type type;

  };

  template<class RET, CALL_TEMPLATE_ARGS> 

  RET call(CALL_FORMAL_ARGS) const { 

    BOOST_STATIC_ASSERT(boost::is_reference<RET>::value); 

    CALL_USE_ARGS; // does nothing, prevents warnings for unused args

    return a; 

  }

};

template<> struct placeholder<SECOND> {

  template<class SigArgs> struct sig {

    typedef typename detail::get_element_or_null_type<1, SigArgs>::type type;

  };

  template<class RET, CALL_TEMPLATE_ARGS> 

  RET call(CALL_FORMAL_ARGS) const { CALL_USE_ARGS; return b; }

};

template<> struct placeholder<THIRD> {

  template<class SigArgs> struct sig {

    typedef typename detail::get_element_or_null_type<2, SigArgs>::type type;

  };

  template<class RET, CALL_TEMPLATE_ARGS> 

  RET call(CALL_FORMAL_ARGS) const { CALL_USE_ARGS; return c; }

};

template<> struct placeholder<EXCEPTION> {

  template<class SigArgs> struct sig {

    typedef typename detail::get_element_or_null_type<3, SigArgs>::type type;

  };

  template<class RET, CALL_TEMPLATE_ARGS> 

  RET call(CALL_FORMAL_ARGS) const { CALL_USE_ARGS; return env; }

};

typedef const lambda_functor<placeholder<FIRST> >  placeholder1_type;

typedef const lambda_functor<placeholder<SECOND> > placeholder2_type;

typedef const lambda_functor<placeholder<THIRD> >  placeholder3_type;

///////////////////////////////////////////////////////////////////////////////

// free variables are lambda_functors. This is to allow uniform handling with 

// other lambda_functors.

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

// -- lambda_functor NONE ------------------------------------------------

template <class T>

class lambda_functor : public T 

{

BOOST_STATIC_CONSTANT(int, arity_bits = get_arity<T>::value);

public:

  typedef T inherited;

  lambda_functor() {}

  lambda_functor(const lambda_functor& l) : inherited(l) {}

  lambda_functor(const T& t) : inherited(t) {}

  template <class SigArgs> struct sig {

    typedef typename inherited::template 

      sig<typename SigArgs::tail_type>::type type;

  };

  // Note that this return type deduction template is instantiated, even 

  // if the nullary 

  // operator() is not called at all. One must make sure that it does not fail.

  typedef typename 

    inherited::template sig<null_type>::type

      nullary_return_type;

  nullary_return_type operator()() const { 

    return inherited::template 

      call<nullary_return_type>

        (cnull_type(), cnull_type(), cnull_type(), cnull_type()); 

  }

  template<class A>

  typename inherited::template sig<tuple<A&> >::type

  operator()(A& a) const { 

    return inherited::template call<

      typename inherited::template sig<tuple<A&> >::type

    >(a, cnull_type(), cnull_type(), cnull_type());

  }

  template<class A, class B>

  typename inherited::template sig<tuple<A&, B&> >::type

  operator()(A& a, B& b) const { 

    return inherited::template call<

      typename inherited::template sig<tuple<A&, B&> >::type

    >(a, b, cnull_type(), cnull_type()); 

  }

  template<class A, class B, class C>

  typename inherited::template sig<tuple<A&, B&, C&> >::type

  operator()(A& a, B& b, C& c) const

  { 

    return inherited::template call<

      typename inherited::template sig<tuple<A&, B&, C&> >::type

    >(a, b, c, cnull_type()); 

  }

  // for internal calls with env

  template<CALL_TEMPLATE_ARGS>

  typename inherited::template sig<tuple<CALL_REFERENCE_TYPES> >::type

  internal_call(CALL_FORMAL_ARGS) const { 

     return inherited::template 

       call<typename inherited::template 

         sig<tuple<CALL_REFERENCE_TYPES> >::type>(CALL_ACTUAL_ARGS); 

  }

  template<class A>

  const lambda_functor<lambda_functor_base<

                  other_action<assignment_action>,

                  boost::tuple<lambda_functor,

                  typename const_copy_argument <const A>::type> > >

  operator=(const A& a) const {

    return lambda_functor_base<

                  other_action<assignment_action>,

                  boost::tuple<lambda_functor,

                  typename const_copy_argument <const A>::type> >

     (  boost::tuple<lambda_functor,

             typename const_copy_argument <const A>::type>(*this, a) );

  }

  template<class A> 

  const lambda_functor<lambda_functor_base< 

                  other_action<subscript_action>, 

                  boost::tuple<lambda_functor, 

                        typename const_copy_argument <const A>::type> > > 

  operator[](const A& a) const { 

    return lambda_functor_base< 

                  other_action<subscript_action>, 

                  boost::tuple<lambda_functor, 

                        typename const_copy_argument <const A>::type> >

     ( boost::tuple<lambda_functor, 

             typename const_copy_argument <const A>::type>(*this, a ) ); 

  } 

};

} // namespace lambda

} // namespace boost

#endif