Re: comparator in match pattern

[Damien Mattei]

thank you, ok , i understand ,my Scheme+ redefined <> to not = , this
was the problem, i apologize

On Wed, Jun 28, 2023 at 5:27 PM Vivien Kraus <vivien@planete-kraus.eu> wrote:
>
> Le mercredi 28 juin 2023 à 17:10 +0200, Damien Mattei a écrit :
> > 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
>
> It works on my side (see screenshot). You did not quote the module
> import line in your reply, did you forget to paste it?
>
> (use-modules (ice-9 match) (srfi srfi-26))
>
> Otherwise it is likely a problem with your guile installation, and I
> can’t really help.
>
> > and / is  not a variable , it is simply a separator , the / procedure
> > too,and it is not quoted
>
> I do not understand. Do you want to match against the '/ symbol or the
> variable/procedure bound to "/"?
>
> If you want to match against something that is bound to "/", then the
> cut-equal solution is relevant. If you want to match against the /
> symbol, then you can do either one of these:
>
> (use-modules (ice-9 match))
> (match (list 1 '/)
>   (`(,c /)
>    c))
>
> or
>
> (use-modules (ice-9 match))
> (match (list 1 '/)
>   ((c '/)
>    c))
>
> > in Racket this works:
> >
> > (match (list container index1-or-keyword index2-or-keyword)
> >
> >           ((list c (== /) (== /)) (displayln "T[/ /]"))
>
> This is not a self-contained example, I don’t know what is index*-or-
> keyword. Is it the division function or whatever is bound to / at that
> time? The / symbol?
>
> Vivien