On Wed, 14 Nov 2001, Sean Russell wrote:

> Robert Feldt wrote:
> 
> > BTW, anyone got a XML grammar out there? Would be fun to try and generate
> > a parser for it in the Rockit  0.4 series...
> 
> No, but it should be pretty easy to extract it from the spec.  That's what 
> I did with XPath, to create that grammar you and I have been discussing.
> 
> I'm still stuck on the excludes, though.  I'm not sure how to rewrite the 
> grammar to get a BNF rule:
> 
>         something := every_token - but_this
> 
You could try a trick with Regexps, the "zero width negative
lookahead". Essentially

    /(?!but_this_tokens)(every_token)/

but you have to fill in the details.

Example is

   /(?!a|bc)(\w+)/

which would be

  something -> words - specials
  words -> /\w+/
  specials -> 'a' | 'bc'

/Robert