Re: comparator in match pattern

[Damien Mattei]

Vivien , your solution is not working:

(let ((/ 42))
  (match (list 1 42)
    ((c (? (cut equal? <> /)))
     c)))
;;; <stdin>:30:2: warning: wrong number of arguments to `#<tree-il
(lambda () (lambda-case ((() #f #f #f () ()) (call (toplevel equal?)
(toplevel <>) (lexical / /-1dff1b83541ce327-407)))))>'
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Wrong number of arguments to 42

and / is  not a variable , it is simply a separator , the / procedure
too,and it is not quoted

in Racket this works:

(match (list container index1-or-keyword index2-or-keyword)

          ((list c (== /) (== /)) (displayln "T[/ /]"))

i can not find an equivalent in Guile:

(match (list 1 /) ((list c (? (cut equal? <> /))) 'cool))
;;; <stdin>:38:0: warning: wrong number of arguments to `#<tree-il
(lambda () (lambda-case ((() #f #f #f () ()) (call (toplevel equal?)
(toplevel <>) (toplevel /)))))>'

i do not understand the syntax.

i can not use the ther solutions with backquote or quote because the
infix parser give / not '/ to my procedures. I have solutions without
match, using cond but they are more long to code and less readable.

On Wed, Jun 28, 2023 at 3:51 PM Vivien Kraus <vivien@planete-kraus.eu> wrote:
>
> Le mercredi 28 juin 2023 à 15:51 +0200, Vivien Kraus a écrit :
> > So, you want to match against the / symbol, not the value of a
> > variable
> > named /?
>
> Sorry, I misread. You actually have a variable named /.
>
> So this code is the only relevant one:
>
> (use-modules (ice-9 match) (srfi srfi-26))
> (let ((/ 42))
>   (match (list 1 42)
>     ((c (? (cut equal? <> /)))
>      c)))
>
> Vivien