Re: Nyacc question: where are the actions bound?

[Matt Wette <matt.wette@gmail.com>]

On 3/8/20 3:14 AM, tomas@tuxteam.de wrote:
> Hi,
>
> I'm playing around with Nyacc: I found a first little use case
> to get my feet wet.
>
> First of all, than you, Matt, for this impressive package.
>
> Shamelessly stolen from the minimal example, playground looks
> roughly like this:
>
> #+begin_source scheme
>    (use-modules (nyacc lalr))
>    (use-modules (nyacc lex))
>    (use-modules (nyacc parse))
>    
>    ;; to be used in some ($$ ...) actions:
>    (define (collect arg) (display arg))
>    
>    (define my-grammar
>      (lalr-spec
>       (start my-file)
>       (grammar
>        (my-file
>         (elt-list))
>        ;; more productions, calling out to ($$... collect)
>        (name
>         ($ident)))))
>    
>    (define mach (make-lalr-machine aq-grammar))
>    (define mtab (lalr-match-table mach))
>    (define gen-lexer (make-lexer-generator mtab))
>    (define raw-parse (make-lalr-parser mach))
>    (define (parse) (raw-parse (gen-lexer)))
>    (parse)
> #+end_source
>
> So I defined some function =collect= which will be called from
> actions in the grammar.
>
> My question is: where is the stuff resolved which is mentioned
> in grammar actions? My first experiments indicate that it's
> looked up at (module) top level, as if (grammar ...) greedily
> weaved that in at compile time.
>
> My idea would be to (pre-) define a grammar and to exchange
> the actions later as needed. Or would I have to re-define the
> grammar whenever I change my mind about actions?
>
> Note that I'm still very much in exploratory mode: "you're
> holding it wrong" would be a perfectly adequate answer, as
> would be "your mumblings are pretty unintelligible" :-)
>
> Cheers & thanks
> -- tomás
Hi Tomas, (I apologize for the ascii spelling)
You may be able to do what you want with the following:

(define (parse)
  (let ((raw-parser (make-lalr-parser)))
    (raw-parser (gen-lexer))))