Re: [Boost-users] [Boost] [Spirit] parse_ast, leaf_node_d and skip parser

Subject: Re: [Boost-users] [Boost] [Spirit] parse_ast, leaf_node_d and skip parser
From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2009-11-19 14:20:53

> Using Boost.Spirit, when I group nodes with a leaf_node_d directive and
> call parse_ast, it looks like I get a node whose value includes some
> characters that are supposed to be skipped.
> 
> My questions: am I missing anything? Is this intended? If yes, what am
> I missing (again)? Is there a way to work around this?
> 
> Here is a simple example program (it should compile and demonstrate
> what I mean, with boost 1.39 and 1.40)

The implementation of AST's in Spirit.Classic is known to be slow and buggy
at times. That's one of the reasons why we developed Spirit 2 (now released
with Boost 1.41, but usable with any Boost >= V1.37). 

You should consider switching to the new version! 
Regards Hartmut

-------------------
Meet me at BoostCon
http://boostcon.com

> 
> // BEGIN OF THE PROGRAM
> #include <iostream>
> 
> #include <boost/spirit/include/classic_core.hpp>
> #include <boost/spirit/include/classic_lists.hpp>
> #include <boost/spirit/include/classic_ast.hpp>
> #include <boost/spirit/include/classic_tree_to_xml.hpp>
> 
> namespace bs = boost::spirit::classic;
> 
> template< typename IteratorT >
> class OkGrammar : public bs::grammar< OkGrammar< IteratorT > > {
> public:
>     template< typename ScannerT >
>     struct definition {
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 1 > >
>         start() { return startRule; }
> 
>         definition( const OkGrammar& ) {
>             startRule = bs::list_p( identifier, bs::ch_p( ',' ) );
> 
>             identifier = +bs::alpha_p;
>         }
> 
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 1 > >
> startRule;
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 2 > >
> identifier;
>     };
> };
> 
> template< typename IteratorT >
> class StrangeGrammar : public bs::grammar< StrangeGrammar< IteratorT >
> > {
> public:
>     template< typename ScannerT >
>     struct definition {
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 1 > >
>         start() { return startRule; }
> 
>         definition( const StrangeGrammar& ) {
>             startRule = bs::list_p( identifier, bs::ch_p( ',' ) );
> 
>             identifier = bs::leaf_node_d[ +bs::alpha_p ];
>         }
> 
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 1 > >
> startRule;
>         bs::rule< ScannerT, bs::parser_context<>, bs::parser_tag< 2 > >
> identifier;
>     };
> };
> 
> int main( int argc, char *argv[] ) {
>     std::string input = "     Hello    ,    wor  ,  ld    ";
> 
>     std::map< bs::parser_id, std::string > ruleNames;
>     ruleNames[ 1 ] = "startRule";
>     ruleNames[ 2 ] = "identifier";
> 
>     typedef std::string::const_iterator iterator;
>     iterator first = input.begin();
>     iterator last = input.end();
> 
>     bs::tree_parse_info< iterator > info = bs::ast_parse(
>         first,
>         last,
>         OkGrammar< iterator >(),
>         +bs::space_p );
>     bs::tree_to_xml( std::cout, info.trees, input, ruleNames );
> 
>     std::cout << std::endl;
> 
>     info = bs::ast_parse(
>         first,
>         last,
>         StrangeGrammar< iterator >(),
>         +bs::space_p );
>     bs::tree_to_xml( std::cout, info.trees, input, ruleNames ); } //
> END OF THE PROGRAM
> 
> Here is the output:
> <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE parsetree SYSTEM
> "parsetree.dtd">
> <!--      Hello    ,    wor  ,  ld     --> <parsetree version="1.0">
>     <parsenode rule="startRule">
>         <parsenode rule="identifier">
>             <parsenode>
>                 <value>H</value>
>             </parsenode>
>             <parsenode>
>                 <value>e</value>
>             </parsenode>
>             <parsenode>
>                 <value>l</value>
>             </parsenode>
>             <parsenode>
>                 <value>l</value>
>             </parsenode>
>             <parsenode>
>                 <value>o</value>
>             </parsenode>
>         </parsenode>
>         <parsenode>
>             <value>,</value>
>         </parsenode>
>         <parsenode rule="identifier">
>             <parsenode>
>                 <value>w</value>
>             </parsenode>
>             <parsenode>
>                 <value>o</value>
>             </parsenode>
>             <parsenode>
>                 <value>r</value>
>             </parsenode>
>         </parsenode>
>         <parsenode>
>             <value>,</value>
>         </parsenode>
>         <parsenode rule="identifier">
>             <parsenode>
>                 <value>l</value>
>             </parsenode>
>             <parsenode>
>                 <value>d</value>
>             </parsenode>
>         </parsenode>
>     </parsenode>
> </parsetree>
> 
> <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE parsetree SYSTEM
> "parsetree.dtd">
> <!--      Hello    ,    wor  ,  ld     --> <parsetree version="1.0">
>     <parsenode rule="startRule">
>         <parsenode rule="identifier">
>             <value>Hello</value>
>         </parsenode>
>         <parsenode>
>             <value>,</value>
>         </parsenode>
>         <parsenode rule="identifier">
>             <value>    wor</value>
>         </parsenode>
>         <parsenode>
>             <value>,</value>
>         </parsenode>
>         <parsenode rule="identifier">
>             <value>  ld</value>
>         </parsenode>
>     </parsenode>
> </parsetree>
> 
> In the first xml tree, there are no node with spaces, while in the
> second, the identifiers do have spaces.
> 
> Thank you for your help,
> --
> Vincent Jacques
> 
> "S'il n'y a pas de solution, c'est qu'il n'y a pas de problème"
>            Devise Shadock