comparator in match pattern

comparator in match pattern

[Damien Mattei]

hello

does it exists in Guile something like == in Racket,
documented here:
https://docs.racket-lang.org/reference/match.html#%28form._%28%28lib._racket%2Fmatch..rkt%29._~3d~3d%29%29

that allows some code like that:

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

          ((list c (== /) (== /)) (displayln "T[/ /]"))
          ((list c i1 (== /)) (displayln "T[i1 /]"))
          ((list c (== /) i2) (displayln "T[/ i2]"))
          ((list c i1 i2) (let ((value expr)) ;; to avoid compute it twice

                ;; normal case
                (if (vector? c)
                    (function-array-n-dim-set! c value (reverse (list
i1 i2))) ;;(array-n-dim-set! array value i1 i2)
                    (array-set! c i1 i2 value))

                value)))

Regards,

Damien

Re: comparator in match pattern

[Vivien Kraus]

Hello!

Le mercredi 28 juin 2023 à 10:44 +0200, Damien Mattei a écrit :
> does it exists in Guile something like == in Racket,
> documented here:
> https://docs.racket-lang.org/reference/match.html#%28form._%28%28lib._racket%2Fmatch..rkt%29._~3d~3d%29%29

From what I understand, (== something) would be translated as (? (cut
equal? <> something)) if you import srfi-26 for cut (or cute, if
something needs to be evaluated once).

Vivien

Re: comparator in match pattern

[Damien Mattei]

hello
i do not understand how i can do that with match:

scheme@(guile-user)> (use-modules (ice-9 match))
scheme@(guile-user)> (match (list 1 /) ((list c (cut equal? <> /))
'cool) ((list c t) 'not_cool))
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Throw to key `match-error' with args `("match" "no matching pattern"
(1 #<procedure / (#:optional _ _ . _)>))'.

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,q
scheme@(guile-user)> (match (list 1 /) ((? (cut equal? <> /)) 'cool)
((list c t) 'not_cool))
;;; <stdin>:23:0: warning: wrong number of arguments to `#<tree-il
(lambda () (lambda-case ((() #f #f #f () ()) (call (toplevel equal?)
(toplevel <>) (toplevel /)))))>'
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Wrong number of arguments to (1 #<procedure / (#:optional _ _ . _)>)

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.


On Wed, Jun 28, 2023 at 10:52 AM Vivien Kraus <vivien@planete-kraus.eu> wrote:
>
> Hello!
>
> Le mercredi 28 juin 2023 à 10:44 +0200, Damien Mattei a écrit :
> > does it exists in Guile something like == in Racket,
> > documented here:
> > https://docs.racket-lang.org/reference/match.html#%28form._%28%28lib._racket%2Fmatch..rkt%29._~3d~3d%29%29
>
> From what I understand, (== something) would be translated as (? (cut
> equal? <> something)) if you import srfi-26 for cut (or cute, if
> something needs to be evaluated once).
>
> Vivien

Re: comparator in match pattern

[Vivien Kraus]

Le mercredi 28 juin 2023 à 15:38 +0200, Damien Mattei a écrit :
> scheme@(guile-user)> (use-modules (ice-9 match))
> scheme@(guile-user)> (match (list 1 /) ((list c (cut equal? <> /))

So, you want to match against the / symbol, not the value of a variable
named /?

The simplest case would be to use quasiquote/unquote syntax in the
pattern:

(match (list 1 '/) 
  (`(,c /) 
   c))

should give: 1, the value of c

If you don’t understand quasiquote/unquote, you can use the slightly
uglier:

(match (list 1 '/) 
  ((c '/) 
   c))

If / is the name of a variable (why not), you can do:

(use-modules (srfi srfi-26))
(let ((/ 42)) 
  (match (list 1 42) 
    ((c (? (cut equal? <> /))) 
     c)))

In any case, no need to write "list" in the pattern.

Vivien

Re: comparator in match pattern

[Vivien Kraus]

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

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

Re: comparator in match pattern

[Vivien Kraus]

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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

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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

Re: comparator in match pattern

[Damien Mattei]

seems to works now:

scheme@(guile-user)> (match (list 1 /) ((c (? (cut equal? <> /))) 'cool))
$2 = cool

On Wed, Jun 28, 2023 at 9:47 PM Damien Mattei <damien.mattei@gmail.com> wrote:
>
> 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