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Boost-Commit : |
Subject: [Boost-commit] svn:boost r53763 - trunk/boost/spirit/home/lex
From: hartmut.kaiser_at_[hidden]
Date: 2009-06-08 20:31:10
Author: hkaiser
Date: 2009-06-08 20:31:09 EDT (Mon, 08 Jun 2009)
New Revision: 53763
URL: http://svn.boost.org/trac/boost/changeset/53763
Log:
Spirit: added placeholders for lexer semantic actions
Added:
trunk/boost/spirit/home/lex/argument.hpp (contents, props changed)
Added: trunk/boost/spirit/home/lex/argument.hpp
==============================================================================
--- (empty file)
+++ trunk/boost/spirit/home/lex/argument.hpp 2009-06-08 20:31:09 EDT (Mon, 08 Jun 2009)
@@ -0,0 +1,239 @@
+// Copyright (c) 2001-2009 Hartmut Kaiser
+// Copyright (c) 2001-2009 Joel de Guzman
+//
+// 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)
+
+#if !defined(BOOST_SPIRIT_LEX_ARGUMENT_JUNE_07_2009_1106AM)
+#define BOOST_SPIRIT_LEX_ARGUMENT_JUNE_07_2009_1106AM
+
+#if defined(_MSC_VER)
+#pragma once
+#endif
+
+#include <boost/spirit/home/phoenix/core/actor.hpp>
+#include <boost/spirit/home/phoenix/core/argument.hpp>
+#include <boost/spirit/home/phoenix/core/compose.hpp>
+#include <boost/spirit/home/phoenix/core/value.hpp>
+#include <boost/spirit/home/phoenix/core/as_actor.hpp>
+#include <boost/spirit/home/phoenix/operator/self.hpp>
+#include <boost/spirit/home/support/string_traits.hpp>
+#include <boost/fusion/include/at.hpp>
+#include <boost/mpl/at.hpp>
+#include <boost/mpl/bool.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/remove_const.hpp>
+#include <boost/utility/enable_if.hpp>
+
+///////////////////////////////////////////////////////////////////////////////
+namespace boost { namespace spirit
+{
+ ///////////////////////////////////////////////////////////////////////////
+ // The state_getter is a Phoenix actor used to access the name of the
+ // current lexer state by calling get_state_name() on the context (which
+ // is the 4th parameter to any lexer semantic actions).
+ //
+ // This Phoenix actor is invoked whenever the placeholder '_state' is used
+ // as a rvalue inside a lexer semantic action:
+ //
+ // lex::token_def<> identifier = "[a-zA-Z_][a-zA-Z0-9_]*";
+ // this->self = identifier [ std::cout << _state ];
+ //
+ // The example shows how to print the lexer state after matching a token
+ // 'identifier'.
+ struct state_getter
+ {
+ typedef mpl::true_ no_nullary;
+
+ template <typename Env>
+ struct result
+ {
+ typedef typename
+ remove_const<
+ typename mpl::at_c<typename Env::args_type, 4>::type
+ >::type
+ context_type;
+
+ typedef typename context_type::state_name_type type;
+ };
+
+ template <typename Env>
+ typename result<Env>::type
+ eval(Env const& env) const
+ {
+ return fusion::at_c<4>(env.args()).get_state_name();
+ }
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // The state_setter is a Phoenix actor used to change the name of the
+ // current lexer state by calling set_state_name() on the context (which
+ // is the 4th parameter to any lexer semantic actions).
+ //
+ // This Phoenix actor is invoked whenever the placeholder '_state' is used
+ // as a lvalue inside a lexer semantic action:
+ //
+ // lex::token_def<> identifier = "[a-zA-Z_][a-zA-Z0-9_]*";
+ // this->self = identifier [ _state = "SOME_LEXER_STATE" ];
+ //
+ // The example shows how to change the lexer state after matching a token
+ // 'identifier'.
+ template <typename Actor>
+ struct state_setter
+ {
+ typedef mpl::true_ no_nullary;
+
+ template <typename Env>
+ struct result
+ {
+ typedef void type;
+ };
+
+ template <typename Env>
+ void eval(Env const& env) const
+ {
+ fusion::at_c<4>(env.args()).set_state_name(
+ traits::get_c_string(actor_()));
+ }
+
+ state_setter(Actor const& actor)
+ : actor_(actor) {}
+
+ Actor actor_;
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // The state_context is used as a noop Phoenix actor to create the
+ // placeholder '_state' (see below). It is a noop actor because it is used
+ // as a placeholder only, while it is being converted either to a
+ // state_getter (if used as a rvalue) or to a state_setter (if used as a
+ // lvalue). The conversion is achieved by specializing and overloading a
+ // couple of the Phoenix templates and functions from the Phoenix
+ // expression composition engine (see the end of this file).
+ struct state_context
+ {
+ typedef mpl::true_ no_nullary;
+
+ template <typename Env>
+ struct result
+ {
+ typedef unused_type type;
+ };
+
+ template <typename Env>
+ unused_type
+ eval(Env const& env) const
+ {
+ return unused;
+ }
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // The eoi_getter is used to create the _eoi placeholder, which is a
+ // Phoenix actor used to access the end of input iterator pointing to the
+ // end of the underlying input sequence.
+ //
+ // This actor is invoked whenever the placeholder '_eoi' is used in a
+ // lexer semantic action:
+ //
+ // lex::token_def<> identifier = "[a-zA-Z_][a-zA-Z0-9_]*";
+ // this->self = identifier
+ // [ std::cout << construct_<std::string>(_end, _eoi) ];
+ //
+ // The example shows how to use _eoi to print all remaining input after
+ // matching a token 'identifier'.
+ struct eoi_getter
+ {
+ typedef mpl::true_ no_nullary;
+
+ template <typename Env>
+ struct result
+ {
+ typedef typename
+ remove_const<
+ typename mpl::at_c<typename Env::args_type, 4>::type
+ >::type
+ context_type;
+
+ typedef typename context_type::base_iterator_type const& type;
+ };
+
+ template <typename Env>
+ typename result<Env>::type
+ eval(Env const& env) const
+ {
+ return fusion::at_c<4>(env.args()).get_eoi();
+ }
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // '_start' and '_end' may be used to access the start and the end of
+ // the matched sequence of the current token
+ phoenix::actor<phoenix::argument<0> > const _start = phoenix::argument<0>();
+ phoenix::actor<phoenix::argument<1> > const _end = phoenix::argument<1>();
+
+ // We are reusing the placeholder '_pass' to access and change the pass
+ // status of the current match (see support/argument.hpp for its
+ // definition).
+
+ // '_tokenid' may be used to access and change the tokenid of the current
+ // token
+ phoenix::actor<phoenix::argument<3> > const _tokenid = phoenix::argument<3>();
+
+ // _state may be used to access and change the name of the current lexer
+ // state
+ phoenix::actor<state_context> const _state = state_context();
+
+ // '_eoi' may be used to access the end of input iterator of the input
+ // stream used by the lexer to match tokens from
+ phoenix::actor<eoi_getter> const _eoi = eoi_getter();
+
+}}
+
+///////////////////////////////////////////////////////////////////////////////
+namespace boost { namespace phoenix
+{
+ ///////////////////////////////////////////////////////////////////////////
+ // The specialization of as_actor_base<> below is needed to convert all
+ // occurrences of _state in places where it's used as a rvalue into the
+ // proper Phoenix actor (spirit::state_getter) accessing the lexer state.
+ template<>
+ struct as_actor_base<actor<spirit::state_context> >
+ {
+ typedef spirit::state_getter type;
+
+ static spirit::state_getter
+ convert(actor<spirit::state_context>)
+ {
+ return spirit::state_getter();
+ }
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // The specialization of as_composite<> below is needed to integrate the
+ // overload of the compose() function into Phoenix expression composition
+ // engine.
+ template <typename RHS>
+ struct as_composite<assign_eval, actor<spirit::state_context>, RHS>
+ {
+ typedef spirit::state_setter<typename as_actor<RHS>::type> type;
+ };
+
+ ///////////////////////////////////////////////////////////////////////////
+ // The compose function overload allows to convert all occurences of
+ // _state in places where it's used as a lvalue into the proper Phoenix
+ // actor (spirit::state_setter) allowing to change the lexer state.
+ template <typename EvalPolicy, typename RHS>
+ inline spirit::state_setter<typename as_actor<RHS>::type>
+ compose(actor<spirit::state_context>, RHS const& rhs
+ , typename enable_if<is_same<EvalPolicy, assign_eval> >::type* = NULL)
+ {
+ typedef typename as_actor<RHS>::type actor_type;
+ return spirit::state_setter<actor_type>(as_actor<RHS>::convert(rhs));
+ }
+
+}}
+
+#undef SPIRIT_DECLARE_ARG
+#endif
+
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