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- // Copyright (c) 2001-2010 Hartmut Kaiser
- //
- // 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)
- // This example is the equivalent to the following lex program:
- //
- // %{
- // /* INITIAL is the default start state. COMMENT is our new */
- // /* state where we remove comments. */
- // %}
- //
- // %s COMMENT
- // %%
- // <INITIAL>"//".* ;
- // <INITIAL>"/*" BEGIN COMMENT;
- // <INITIAL>. ECHO;
- // <INITIAL>[\n] ECHO;
- // <COMMENT>"*/" BEGIN INITIAL;
- // <COMMENT>. ;
- // <COMMENT>[\n] ;
- // %%
- //
- // main()
- // {
- // yylex();
- // }
- //
- // Its purpose is to strip comments out of C code.
- //
- // Additionally this example demonstrates the use of lexer states to structure
- // the lexer definition.
- // #define BOOST_SPIRIT_LEXERTL_DEBUG
- #include <boost/config/warning_disable.hpp>
- #include <boost/spirit/include/qi.hpp>
- #include <boost/spirit/include/lex_lexertl.hpp>
- #include <boost/spirit/include/phoenix_operator.hpp>
- #include <boost/spirit/include/phoenix_container.hpp>
- #include <iostream>
- #include <string>
- #include "example.hpp"
- using namespace boost::spirit;
- ///////////////////////////////////////////////////////////////////////////////
- // Token definition: We use the lexertl based lexer engine as the underlying
- // lexer type.
- ///////////////////////////////////////////////////////////////////////////////
- enum tokenids
- {
- IDANY = lex::min_token_id + 10
- };
- template <typename Lexer>
- struct strip_comments_tokens : lex::lexer<Lexer>
- {
- strip_comments_tokens()
- : strip_comments_tokens::base_type(lex::match_flags::match_default)
- {
- // define tokens and associate them with the lexer
- cppcomment = "\"//\"[^\n]*"; // '//[^\n]*'
- ccomment = "\"/*\""; // '/*'
- endcomment = "\"*/\""; // '*/'
- // The following tokens are associated with the default lexer state
- // (the "INITIAL" state). Specifying 'INITIAL' as a lexer state is
- // strictly optional.
- this->self.add
- (cppcomment) // no explicit token id is associated
- (ccomment)
- (".", IDANY) // IDANY is the token id associated with this token
- // definition
- ;
- // The following tokens are associated with the lexer state "COMMENT".
- // We switch lexer states from inside the parsing process using the
- // in_state("COMMENT")[] parser component as shown below.
- this->self("COMMENT").add
- (endcomment)
- (".", IDANY)
- ;
- }
- lex::token_def<> cppcomment, ccomment, endcomment;
- };
- ///////////////////////////////////////////////////////////////////////////////
- // Grammar definition
- ///////////////////////////////////////////////////////////////////////////////
- template <typename Iterator>
- struct strip_comments_grammar : qi::grammar<Iterator>
- {
- template <typename TokenDef>
- strip_comments_grammar(TokenDef const& tok)
- : strip_comments_grammar::base_type(start)
- {
- // The in_state("COMMENT")[...] parser component switches the lexer
- // state to be 'COMMENT' during the matching of the embedded parser.
- start = *( tok.ccomment
- >> qi::in_state("COMMENT")
- [
- // the lexer is in the 'COMMENT' state during
- // matching of the following parser components
- *token(IDANY) >> tok.endcomment
- ]
- | tok.cppcomment
- | qi::token(IDANY) [ std::cout << _1 ]
- )
- ;
- }
- qi::rule<Iterator> start;
- };
- ///////////////////////////////////////////////////////////////////////////////
- int main(int argc, char* argv[])
- {
- // iterator type used to expose the underlying input stream
- typedef std::string::iterator base_iterator_type;
- // lexer type
- typedef
- lex::lexertl::lexer<lex::lexertl::token<base_iterator_type> >
- lexer_type;
- // iterator type exposed by the lexer
- typedef strip_comments_tokens<lexer_type>::iterator_type iterator_type;
- // now we use the types defined above to create the lexer and grammar
- // object instances needed to invoke the parsing process
- strip_comments_tokens<lexer_type> strip_comments; // Our lexer
- strip_comments_grammar<iterator_type> g (strip_comments); // Our parser
- // Parsing is done based on the token stream, not the character
- // stream read from the input.
- std::string str (read_from_file(1 == argc ? "strip_comments.input" : argv[1]));
- base_iterator_type first = str.begin();
- bool r = lex::tokenize_and_parse(first, str.end(), strip_comments, g);
- if (r) {
- std::cout << "-------------------------\n";
- std::cout << "Parsing succeeded\n";
- std::cout << "-------------------------\n";
- }
- else {
- std::string rest(first, str.end());
- std::cout << "-------------------------\n";
- std::cout << "Parsing failed\n";
- std::cout << "stopped at: \"" << rest << "\"\n";
- std::cout << "-------------------------\n";
- }
- std::cout << "Bye... :-) \n\n";
- return 0;
- }
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