Multiple Yacc-style Parsers in one application?

Multiple Yacc-style Parsers in one application?

[Steve Stevenson]

Good morning.

I'm interested in hearing experiences from people who have used
multiple yacc parsers in one application. I assume that they would
share one lexer buffer (but maybe not). Do you have to manipulate the
lexical world to deal with the one-lookahead?

Any experiences, stories, etc, greatly appreciated.

Best regards,

steve
-----
Steve (really "D. E.") Stevenson           Assoc Prof
Department of Computer Science, Clemson,   (864)656-5880.mabell
Support V&V mailing list: ivandv@cs.clemson.edu

Re: Multiple Yacc-style Parsers in one application?

[Chris Tilt]

Steve,

When I discovered the lex/yacc tools for caml I was very impressed.
They are implemented in a completely functional way, with no magic
entry points or expected symbols, etc. We have an application with
two yacc parsers, each with their own lexer. Since the yacc-created
parser takes a lex buffer and a lexer function, you can build any
number of co-existing parsers. Each lexer also has its own name
space, so it's very different from the old C yacc/lex experience.

As a partial example of how the machinery works, here is a code
snippet (with no exception handling, which you need). The returned
document is of the type returned by the function "Xmlparse.document".
The cool part is that *any* of the left-hand-side productions can
be used as entry points for your parser. This makes it trivial to
parse, e.g. document fragments in this XML example.

let doc =
  let lexbuf = Lexing.from_channel in_chan
in
  Xmlparse.document Xmlscan.scan lexbuf

-Chris

P.S. Thanks to the CAML team for these great tools. We are building
our second industrial product with CAML 3.0 release.

Steve Stevenson wrote:
> 
> Good morning.
> 
> I'm interested in hearing experiences from people who have used
> multiple yacc parsers in one application. I assume that they would
> share one lexer buffer (but maybe not). Do you have to manipulate the
> lexical world to deal with the one-lookahead?
> 
> Any experiences, stories, etc, greatly appreciated.
> 
> Best regards,
> 
> steve
> -----
> Steve (really "D. E.") Stevenson           Assoc Prof
> Department of Computer Science, Clemson,   (864)656-5880.mabell
> Support V&V mailing list: ivandv@cs.clemson.edu

-- 
Chris Tilt			mailto:cet@webcriteria.com
CTO, WebCriteria, Inc.		http://www.webcriteria.com

Re: Multiple Yacc-style Parsers in one application?

[Christian Rinderknecht]

Hello Steve,

Last year I wrote in OCaml a software that had to deal with multiple
output/input files of a commercial tool, and hence needed up to six lexers
and parsers. The different formats were rather close (both lexically and
syntactically), but I wasn't able to share the lexers and the parsers
rules because:
  1) ocamllex generates an "open <Parser module name>" directive;
  2) ocamlyacc doesn't allow rule sharing.
Nevertheless, I shared a lot of semantic actions (defined in standalone
modules).

The first point could be solved if ocamllex produced a functor whose
argument signature would constrain the abstract syntax tree, but I am not
sure the underlying implementation of lexer buffers would then behave
soundly.

Best regards,


Christian

--------------------------------------------------------------------
Christian Rinderknecht          Christian.Rinderknecht@polyspace.com
PolySpace Technologies          Tel: 04.76.61.54.17
c/o INRIA                       Fax: 04.76.61.54.09
655, Av. de l'Europe            http://www.polyspace.com/
F-38330 Montbonnot St Martin

On Fri, 23 Jun 2000, Steve Stevenson wrote:

> I'm interested in hearing experiences from people who have used
> multiple yacc parsers in one application. I assume that they would
> share one lexer buffer (but maybe not). Do you have to manipulate the
> lexical world to deal with the one-lookahead?