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[Caml-list] On ocamlyacc and ocamllex
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Date: -- (:)
From: Christian Lindig <lindig@e...>
Subject: Re: [Caml-list] On ocamlyacc and ocamllex
On Sun, Sep 23, 2001 at 10:32:23PM +0300, Vesa Karvonen wrote:
> From: "Christian Lindig" <lindig@eecs.harvard.edu>
> I'd prefer that the lexer generator would be extended so that additional
> arguments could be added in a manner similar to this:
> 
>     rule token map = parse
>         eof         { P.EOF }
>       | ws+         { token map lexbuf }
>       | tab         { tab map lexbuf; token map lexbuf }
>       | nl          { nl map lexbuf ; token map lexbuf }
>       | nl '#'      { line map lexbuf 0; token map lexbuf }
>        ...

I lobbied for this three years ago and had a patch for ocamllex:

    http://www.eecs.harvard.edu/~lindig/software/lex-patch.html

> Can this technique be used for adding context to parsers generated
> using ocamlyacc, too?

I'm not sure what you mean here. A Yacc parser works bottom up - do you
want to inject "context" into the tokens that are received from the
lexer?

> I agree that it may be somewhat easier for the parser generator, but I
> find that separating the token type definition from the grammar
> definition can be justified using quantitative technical arguments.

I agree that this alternative avoids the dependency of the type
definition on the grammar. But I am not sure that manually keeping the
type definition and the %token declarations in the parser in sync is
better than automatic recompiles or a little Make hack.

-- Christian

-- 
Christian Lindig          Harvard University - DEAS
lindig@eecs.harvard.edu   33 Oxford St, MD 242, Cambridge MA 02138
phone: +1 (617) 496-7157  http://www.eecs.harvard.edu/~lindig/
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