[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Bison-like source locations in LALR-parser

From: Ludovic Courtès
Subject: Re: Bison-like source locations in LALR-parser
Date: Wed, 13 Aug 2014 23:01:47 +0200
User-agent: Gnus/5.130011 (Ma Gnus v0.11) Emacs/24.3 (gnu/linux)


Jan Nieuwenhuizen <address@hidden> skribis:

> Ludovic Courtès writes:
>> I don’t think this is needed.  Lexers are expected to use
>> ‘make-lexical-token’ and ‘make-source-location’ from (system base lalr)
>> to preserve source location information.
> I hope you're right...and that's what I tried, but I didn't get it
> working.  Possibly I need to cook-up a small example.
> What I found was that, yes the LEXER has all it needs, but once you
> get to construction rules in the parser; say
>    (interface-spec
>     (interface Identifier lbrace type-list event-list optional-behaviour 
> rbrace) : `(,$1 ,$2 ,$4 ,$5 ,$6))
> all it sees is the values, i.e. strings of the tokens that the lexer
> sees.  The lexer cannot hand tokens to the parser, AFAICS.

Here’s an example:

Note that actually, the ‘location’ produced by does:

  (make-lexical-token type (make-source-location ...)
                      (append value (list (vector line column))))

So the line/column info is also stored alongside the token’s value, and
then access from parser.scm with those cadr calls.

>> Besides, note that lalr.upstream.scm is a copy of the upstream lalr-scm,
>> hosted at <>.
> Yes...that's looks quit dead.  Isn't it?  I can try though...

Well, that’s because it’s “finished.”  :-)

But yeah, it’s worth trying.  Dominique has been responsive and helpful
in the past.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]