On Wed, Jun 05, 2002 at 09:45:29AM -0400, Marcus J. Ranum wrote:
> Sweth Chandramouli wrote:
> >Marcus was doing his
> >version in C, which for performance reasons makes a lot of sense
>
> :) I was doing it in C because it's the only programming language
> I know. :) It wasn't for performance reasons!!!
Understood. I was just saying that you were using C, and
that independent of that, I thought that the use of C would make sense
in the long run for performance reasons. :)
> Lex/Yacc produce static parsers. They're compiler/parser generators
> and I think you'd be taking the wrong approach to use them. What I'd
> suggest is developing a subset of a BNF grammar
A Parse::RecDescent grammar in Perl is almost exactly that.
Case in point, here's a quick P::RD grammar I came up with the other day
to parse shell globbing syntax:
globstring: token(s)
token: metastring | globchar | literal
metastring: escaped_char | character_class
escaped_char: /\\./
character_class: openbracket
[ negation | internal_bracket ]
class_token(s)
closebracket
openbracket: /\[/
negation: /!/
internal_bracket: /[][]/
class_token: escaped_char | character_range | class_char
character_range: /.-./
class_char: /[^]]/
closebracket: /]/
globchar: asterisk | questionmark
asterisk: '*'
questionmark: '?'
literal: /./
. No left recursion, which I think you were worried about
in a different post, and the regexes could just as easily be replaced
with string matches if you really wanted to; I'll address the concerns
about regexes in another post, however. :)
-- Sweth.
--
Sweth Chandramouli Idiopathic Systems Consulting
svcat_private http://www.idiopathic.net/
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