text: // Copyright David Abrahams 2002.
  // 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)
  #ifndef DATA_MEMBERS_DWA2002328_HPP
  # define DATA_MEMBERS_DWA2002328_HPP
  
  # include <boost/python/detail/prefix.hpp>
  
  # include <boost/python/handle.hpp>
  
  # include <boost/python/return_value_policy.hpp>
  # include <boost/python/return_by_value.hpp>
  # include <boost/python/return_internal_reference.hpp>
  # include <boost/python/make_function.hpp>
  
  # include <boost/python/converter/builtin_converters.hpp>
  
  # include <boost/python/detail/indirect_traits.hpp>
  # include <boost/python/detail/not_specified.hpp>
  # include <boost/python/detail/value_arg.hpp>
  
  # include <boost/type_traits/add_const.hpp>
  # include <boost/type_traits/add_reference.hpp>
  # include <boost/type_traits/is_member_pointer.hpp>
  
  # if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
  #  include <boost/type_traits/remove_cv.hpp>
  # endif 
  
  # include <boost/mpl/eval_if.hpp>
  # include <boost/mpl/if.hpp>
  # include <boost/mpl/vector/vector10.hpp>
  
  # include <boost/detail/workaround.hpp>
  
  namespace boost { namespace python { 
  
  //
  // This file defines the make_getter and make_setter function
  // families, which are responsible for turning pointers, references,
  // and pointers-to-data-members into callable Python objects which
  // can be used for attribute access on wrapped classes.
  //
  
  namespace detail
  {
  
    // A small function object which handles the getting and setting of
    // data members.
    template <class Data, class Class>
    struct member
    {
     public:      
        member(Data Class::*which) : m_which(which) {}
        
        Data& operator()(Class& c) const
        {
            return c.*m_which;
        }
  
        void operator()(Class& c, typename value_arg<Data>::type d) const
        {
            c.*m_which = d;
        }
     private:
        Data Class::*m_which;
    };
  
    // A small function object which handles the getting and setting of
    // non-member objects.
    template <class Data>
    struct datum
    {
     public:      
        datum(Data *which) : m_which(which) {}
        
        Data& operator()() const
        {
            return *m_which;
        }
  
        void operator()(typename value_arg<Data>::type d) const
        {
            *m_which = d;
        }
     private:
        Data *m_which;
    };
    
    //
    // Helper metafunction for determining the default CallPolicy to use
    // for attribute access.  If T is a [reference to a] class type X
    // whose conversion to python would normally produce a new copy of X
    // in a wrapped X class instance (as opposed to types such as
    // std::string, which are converted to native Python types, and
    // smart pointer types which produce a wrapped class instance of the
    // pointee type), to-python conversions will attempt to produce an
    // object which refers to the original C++ object, rather than a
    // copy.  See default_member_getter_policy for rationale.
    // 
    template <class T>
    struct default_getter_by_ref
        : mpl::and_<
            mpl::bool_<
                to_python_value<
                    typename value_arg<T>::type
                >::uses_registry
            >
          , indirect_traits::is_reference_to_class<
                typename value_arg<T>::type
            >
         >
    {
    };
  
    // Metafunction computing the default CallPolicy to use for reading
    // data members
    //
    // If it's a regular class type (not an object manager or other
    // type for which we have to_python specializations, use
    // return_internal_reference so that we can do things like
    //    x.y.z =  1
    // and get the right result.
    template <class T>
    struct default_member_getter_policy
      : mpl::if_<
            default_getter_by_ref<T>
          , return_internal_reference<>
          , return_value_policy<return_by_value>
        >
    {};
  
    // Metafunction computing the default CallPolicy to use for reading
    // non-member data.
    template <class T>
    struct default_datum_getter_policy
      : mpl::if_<
            default_getter_by_ref<T>
          , return_value_policy<reference_existing_object>
          , return_value_policy<return_by_value>
        >
    {};
  
    //
    // make_getter helper function family -- These helpers to
    // boost::python::make_getter are used to dispatch behavior.  The
    // third argument is a workaround for a CWPro8 partial ordering bug
    // with pointers to data members.  It should be convertible to
    // mpl::true_ iff the first argument is a pointer-to-member, and
    // mpl::false_ otherwise.  The fourth argument is for compilers
    // which don't support partial ordering at all and should always be
    // passed 0L.
    //
  
  #if BOOST_WORKAROUND(__EDG_VERSION__, <= 238)
    template <class D, class P>
    inline object make_getter(D& d, P& p, mpl::false_, ...);
  #endif
  
    // Handle non-member pointers with policies
    template <class D, class Policies>
    inline object make_getter(D* d, Policies const& policies, mpl::false_, int)
    {
        return python::make_function(
            detail::datum<D>(d), policies, mpl::vector1<D&>()
        );
    }
    
    // Handle non-member pointers without policies
    template <class D>
    inline object make_getter(D* d, not_specified, mpl::false_, long)
    {
        typedef typename default_datum_getter_policy<D>::type policies;
        return detail::make_getter(d, policies(), mpl::false_(), 0);
    }
  
    // Handle pointers-to-members with policies
    template <class C, class D, class Policies>
    inline object make_getter(D C::*pm, Policies const& policies, mpl::true_, int)
    {
  #if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
        typedef typename remove_cv<C>::type Class;
  #else
        typedef C Class;
  #endif 
        return python::make_function(
            detail::member<D,Class>(pm)
          , policies
          , mpl::vector2<D&,Class&>()
        );
    }
        
    // Handle pointers-to-members without policies
    template <class C, class D>
    inline object make_getter(D C::*pm, not_specified, mpl::true_, long)
    {
        typedef typename default_member_getter_policy<D>::type policies;
        return detail::make_getter(pm, policies(), mpl::true_(), 0);
    }
  
    // Handle references
    template <class D, class P>
    inline object make_getter(D& d, P& p, mpl::false_, ...)
    {
        // Just dispatch to the handler for pointer types.
        return detail::make_getter(&d, p, mpl::false_(), 0L);
    }
  
    //
    // make_setter helper function family -- These helpers to
    // boost::python::make_setter are used to dispatch behavior.  The
    // third argument is for compilers which don't support partial
    // ordering at all and should always be passed 0.
    //
  
    
    // Handle non-member pointers
    template <class D, class Policies>
    inline object make_setter(D* p, Policies const& policies, mpl::false_, int)
    {
        return python::make_function(
            detail::datum<D>(p), policies, mpl::vector2<void,D const&>()
        );
    }
  
    // Handle pointers-to-members
    template <class C, class D, class Policies>
    inline object make_setter(D C::*pm, Policies const& policies, mpl::true_, int)
    {
        return python::make_function(
            detail::member<D,C>(pm)
          , policies
          , mpl::vector3<void, C&, D const&>()
        );
    }
  
    // Handle references
    template <class D, class Policies>
    inline object make_setter(D& x, Policies const& policies, mpl::false_, ...)
    {
        return detail::make_setter(&x, policies, mpl::false_(), 0L);
    }
  }
  
  //
  // make_getter function family -- build a callable object which
  // retrieves data through the first argument and is appropriate for
  // use as the `get' function in Python properties .  The second,
  // policies argument, is optional.  We need both D& and D const&
  // overloads in order be able to handle rvalues.
  //
  template <class D, class Policies>
  inline object make_getter(D& d, Policies const& policies)
  {
      return detail::make_getter(d, policies, is_member_pointer<D>(), 0L);
  }
  
  template <class D, class Policies>
  inline object make_getter(D const& d, Policies const& policies)
  {
      return detail::make_getter(d, policies, is_member_pointer<D>(), 0L);
  }
  
  template <class D>
  inline object make_getter(D& x)
  {
      detail::not_specified policy
          = detail::not_specified(); // suppress a SunPro warning
      return detail::make_getter(x, policy, is_member_pointer<D>(), 0L);
  }
  
  #  if !BOOST_WORKAROUND(__EDG_VERSION__, <= 238)
  template <class D>
  inline object make_getter(D const& d)
  {
      detail::not_specified policy
          = detail::not_specified(); // Suppress a SunPro warning
      return detail::make_getter(d, policy, is_member_pointer<D>(), 0L);
  }
  #  endif
  
  //
  // make_setter function family -- build a callable object which
  // writes data through the first argument and is appropriate for
  // use as the `set' function in Python properties .  The second,
  // policies argument, is optional.  We need both D& and D const&
  // overloads in order be able to handle rvalues.
  //
  template <class D, class Policies>
  inline object make_setter(D& x, Policies const& policies)
  {
      return detail::make_setter(x, policies, is_member_pointer<D>(), 0);
  }
  
  template <class D, class Policies>
  inline object make_setter(D const& x, Policies const& policies)
  {
      return detail::make_setter(x, policies, is_member_pointer<D>(), 0);
  }
  
  template <class D>
  inline object make_setter(D& x)
  {
      return detail::make_setter(x, default_call_policies(), is_member_pointer<D>(), 0);
  }
  
  # if !BOOST_WORKAROUND(__EDG_VERSION__, <= 238)
  template <class D>
  inline object make_setter(D const& x)
  {
      return detail::make_setter(x, default_call_policies(), is_member_pointer<D>(), 0);
  }
  # endif
  
  }} // namespace boost::python
  
  #endif // DATA_MEMBERS_DWA2002328_HPP
  