Re: [Boost-users] [Spirit] parse tree node does not get produced with Single character input.

29 Jun 2010

      I know this is old, but it has had no response, I apologize...

On Tue, Jun 8, 2010 at 9:03 AM, Philippe forest
 wrote:
...
Hi,
Greetings,

You should update your Boost, the later versions are vastly better,
allow me to demonstrate:

On Tue, Jun 8, 2010 at 9:03 AM, Philippe forest
 wrote:
...
First of all I would like to state that
spirit =
 str_p("very") >> +ch_p(' ') >>( str_p("nice") | str_p("cool") |
str_p("greate") ) >> +ch_p(' ') >> str_p("parser")
;
In modern Spirit:
  spirit
    =  skip(' ')[lit("very")
    >> (lit("nice")
       |    "cool"
       |    "great")
    )>>"parser"]
    ;
...
So Thanks for that.
But I do face a problem. When assigning ID to nodes of the parse tree.
ex: rule, parser_tag<stringID> >  String;
I've attached a sample to demonstrate the problem.
In short:
The grammar below does not produce a parse tree node with a 'stringID'
when the input is a single character 'a'. As soon as I have 2 or more
characters 'aa' then I get a node stringID.
        definition(
         ExpressionNoStringIDGrammar const& /*self*/)
       {
         Char =
           ch_p('a')
           ;
         String =
           ( +Char )
           ;
         language =
           String
           ;
       }
rule, parser_tag<charID> >         Char;
rule, parser_tag<stringID> >       String;
rule<ScannerT> language;
In modern Spirit, this should work fine:
template<typename Iterator>
class definition : grammar
{
    definition() : definition::base_type(language)
    {
        Char =
            char_('a')
            ;

          String =
            +Char
            ;

          language =
            String
            ;
        }

 rule         Char;
 rule  String;
 rule  language;
}

That will return the parsed string of a's as an std::string.  Look at
the new Spirit, insanely more powerful, and so much easier to use as
well.

http://www.boost.org/doc/libs/1_43_0/libs/spirit/doc/html/index.html

On Tue, Jun 8, 2010 at 9:03 AM, Philippe forest
 wrote:
...
BUT:
If I remove the 'Char' parser and substitute it with ch_p('a') then it
works fine , then I always get a node stringID even with a single input
char.
        definition(
         ExpressionNoStringIDGrammar const& /*self*/)
       {
         String =
           ( +ch_p('a') )
           ;
         language =
           String
           ;
       }
rule, parser_tag<charID> >         Char;
rule, parser_tag<stringID> >       String;
rule<ScannerT> language;
Could anyone either explain me what is going on ?
 - I'm I doing something wrong or is this a bug or works as designed ?

Re: [Boost-users] [Spirit] parse tree node does not get produced with Single character input.

OvermindDL1