/*============================================================================= | |
Copyright (c) 2001-2011 Joel de Guzman | |
http://spirit.sourceforge.net/ | |
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 BOOST_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM | |
#define BOOST_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM | |
#if defined(_MSC_VER) | |
#pragma once | |
#endif | |
#include <boost/proto/proto.hpp> | |
#include <boost/mpl/if.hpp> | |
#include <boost/type_traits/is_base_of.hpp> | |
#include <boost/spirit/home/support/unused.hpp> | |
namespace boost { namespace spirit | |
{ | |
template <typename Domain, typename T, typename Enable = void> | |
struct is_modifier_directive; | |
// Testing if a modifier set includes a modifier T involves | |
// checking for inheritance (i.e. Modifiers is derived from T) | |
template <typename Modifiers, typename T> | |
struct has_modifier | |
: is_base_of<T, Modifiers> {}; | |
// Adding modifiers is done using multi-inheritance | |
template <typename Current, typename New, typename Enable = void> | |
struct compound_modifier : Current, New | |
{ | |
compound_modifier() | |
: Current(), New() {} | |
compound_modifier(Current const& current, New const& new_) | |
: Current(current), New(new_) {} | |
}; | |
// Don't add if New is already in Current | |
template <typename Current, typename New> | |
struct compound_modifier< | |
Current, New, typename enable_if<has_modifier<Current, New> >::type> | |
: Current | |
{ | |
compound_modifier() | |
: Current() {} | |
compound_modifier(Current const& current, New const&) | |
: Current(current) {} | |
}; | |
// Special case if Current is unused_type | |
template <typename New, typename Enable> | |
struct compound_modifier<unused_type, New, Enable> : New | |
{ | |
compound_modifier() | |
: New() {} | |
compound_modifier(unused_type, New const& new_) | |
: New(new_) {} | |
}; | |
// Domains may specialize this modify metafunction to allow | |
// directives to add information to the Modifier template | |
// parameter that is passed to the make_component metafunction. | |
// By default, we return the modifiers untouched | |
template <typename Domain, typename Enable = void> | |
struct modify | |
{ | |
template <typename Sig> | |
struct result; | |
template <typename This, typename Tag, typename Modifiers> | |
struct result<This(Tag, Modifiers)> | |
{ | |
typedef typename remove_const< | |
typename remove_reference<Tag>::type>::type | |
tag_type; | |
typedef typename remove_const< | |
typename remove_reference<Modifiers>::type>::type | |
modifiers_type; | |
typedef typename mpl::if_< | |
is_modifier_directive<Domain, tag_type> | |
, compound_modifier<modifiers_type, tag_type> | |
, Modifiers>::type | |
type; | |
}; | |
template <typename Tag, typename Modifiers> | |
typename result<modify(Tag, Modifiers)>::type | |
operator()(Tag tag, Modifiers modifiers) const | |
{ | |
return op(tag, modifiers, is_modifier_directive<Domain, Tag>()); | |
} | |
template <typename Tag, typename Modifiers> | |
Modifiers | |
op(Tag /*tag*/, Modifiers modifiers, mpl::false_) const | |
{ | |
return modifiers; | |
} | |
template <typename Tag, typename Modifiers> | |
compound_modifier<Modifiers, Tag> | |
op(Tag tag, Modifiers modifiers, mpl::true_) const | |
{ | |
return compound_modifier<Modifiers, Tag>(modifiers, tag); | |
} | |
}; | |
}} | |
namespace boost { namespace proto | |
{ | |
template <typename Domain, typename Enable> | |
struct is_callable<spirit::modify<Domain, Enable> > | |
: mpl::true_ {}; | |
}} | |
#endif |