Re: SD4F: (exist? procedure-**maximum**-arity)

[Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>]

Hello Blake!

You might be interested in this:
https://notabug.org/ZelphirKaltstahl/function-combinators/src/master/notes.org =)

Although I did try to implement things in a purely functional way, going perhaps
a bit too far.

Also "applicable structs" in Guile could prove useful, if you can find any
usable example and are able to adapt to the use-case.

Regards,
Zelphir

On 12/29/21 2:23 AM, Blake Shaw wrote:
> Hiya Guilers,
>
> I've just started Sussman & Hanson's new book "Software Design for Flexibility" and am trying to translate one of the functions from MIT-Scheme to Guile:
>
> #+BEGIN_SRC scheme
> (define (get-arity proc)
>   (or (hash-table-ref/default arity-table proc #f)
>       (let ((a (procedure-arity proc))) ;arity not in table
>         (assert (eqv? (procedure-arity-min a)
>                       (procedure-arity-max a)))
>         (procedure-arity-min a))))
>
> (define arity-table (make-weak-key-hash-table))
> #+END_SRC
>
> So far this has lead me to these associations:
> |------------------------------+--------------------------+-------------------------|
> | MIT                          | Guile                    | Comments                |
> |------------------------------+--------------------------+-------------------------|
> | procedure-arity              | arity                    |                         |
> |------------------------------+--------------------------+-------------------------|
> | hash-table-set!              | hashq-set!               | possibly =hash-set!=    |
> |------------------------------+--------------------------+-------------------------|
> | hash-table-ref/default       | hashq-ref                | possibly =hash-ref=     |
> |                              |                          | or =hash-get-handle=    |
> |------------------------------+--------------------------+-------------------------|
> | make-key-weak-eqv-hash-table | make-weak-key-hash-table | ∃(module) w/eqv-hash?   |
> |                              |                          | think I saw it before   |
> |------------------------------+--------------------------+-------------------------|
> | assert                       | assert                   | in (rnrs base)          |
> |                              | &assertion               | + (ice-9 exceptions)    |
> |                              | assert-macro             | + in (debugging assert) |
> |------------------------------+--------------------------+-------------------------|
> | procedure-arity-min          | procedure-minimum-arity  |                         |
>
> resulting in this translation of the function:
>
> #+BEGIN_SRC scheme
>  (define (get-arity proc)
>     (or (hashq-ref arity-table proc #f)
> 	(let ((a (arity proc)))
> 	  (assert (eqv? (procedure-minimum-arity a)
> 			(**procedure-minimum-arity** a)))
> 	  (procedure-minimum-arity a))))
> #+END_SRC 
>
> So now I'm just left with figuring out a function for getting the **maximum**[1] arity of a procedure, but I'm unsure how to go about this.
>
> I'm a sorta-new schemer and a very new guiler, so I'm unsure where to look... any advice would be appreciated![2]
>
> Thanks & happy hacking,
> Blake
>
> [1] double earmuffs to emphasize its a function I need but dont have
> [2] there is this inquiry already posted, but there was no conclusion https://mail.gnu.org/archive/html/guile-user/2021-05/msg00044.html 
>
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