Tweaking the Skip Parser, was RE: [Boost-users] Spirit 1.6 with VC6

From: Mark Storer (MStorer_at_[hidden])
Date: 2004-06-25 12:18:09

> No chance of switching to 7.1? :-)

Things are looking up.  We just did a project-wide upgrade to... VC7.1.  Problem solved.  I'm now merrily writing rules for my JavaScript parser.  It doesn't have to support the whole language (not for a while, maybe never), I just need to be able to parse out the names and locations of all the functions in a file.  It's for a JavaScript editor built into one of our products, and later we'll be adding auto-completion.  That'll require a more thorough parser, but for now, I'm just after funciton locations.

So far so good... though I'll undoubtedly be quite familiar with the BOOST_SPIRIT_DEBUG* macros before I'm done.

I've got another Spirit question:  I've been adding "*comment" throughout the rules and it's getting tiresome:

  rule<phrase_scanner_t> blockComment = comment_p( "/*", "*/" );
  rule<phrase_scanner_t> lineComment  = comment_p( "//" );
  rule<phrase_scanner_t> comment      = blockComment | lineComment;

Spraying the "comment" rule liberally through my rules is an option...

  rule<phrase_scanner_t> codeBlock    = ch_p('{') >> *(comment | codeBlock | ~ch_p('}')) >> ch_p('}');

... but not an appealing one.  This becomes particularly true once I start working on the auto-completion parser.

  It just occured to me that if the skip parser ate comments for me, it would greatly simplify my rules.  I'd like to tweak the skip parser so it skips over my "comment" rule as well as white space.  I just took a stab at this, but didn't get very far.  I tried:

parse(str, rules, space_p | comment)

but that resulted in a compiler error.  7.1's errors are MUCH easier to read that 6's.  I'm going to like this new compiler.

C:\SDKs\boost_1_31_0\boost\spirit\core\non_terminal\impl\rule.ipp(190): error C2664: 'boost::spirit::impl::abstract_parser<ScannerT,AttrT>::do_parse_virtual' : cannot convert parameter 1 from 'const scanner_t' to 'const boost::spirit::rule<T0>::scanner_t &'
        with
        [
            ScannerT=boost::spirit::rule<boost::spirit::phrase_scanner_t>::scanner_t,
            AttrT=boost::spirit::rule<boost::spirit::phrase_scanner_t>::attr_t
        ]
        and
        [
            T0=boost::spirit::phrase_scanner_t
        ]

Pointing me to the relevant section of the docs is an acceptable answer, though I wouldn't mind a little more info than that. ;)

I'll keep plugging away.  If I come up with an answer, I'll post it to the list.  I'd expect this to be useful to other beginners at the very least.

--Mark Storer
  Senior Software Engineer
  Verity, Inc.