* new match system bug?
@ 2010-09-04 12:38 Stefan Israelsson Tampe
2010-09-04 12:44 ` Ludovic Courtès
0 siblings, 1 reply; 6+ messages in thread
From: Stefan Israelsson Tampe @ 2010-09-04 12:38 UTC (permalink / raw)
To: guile-devel
[-- Attachment #1: Type: text/plain, Size: 257 bytes --]
Hi,
While eating the dogfood of the new match macro I come across a bug
e.g, this does not work!
(match '(a b) ((and x (a ... b)) a))
But using the attached patch, it works!!
Note. This should be interesting for upstreams maintainers.
/Regards
Stefan
[-- Attachment #2: match-gen-ellipses-bug.patch --]
[-- Type: text/x-patch, Size: 2497 bytes --]
diff --git a/module/ice-9/match.scm b/module/ice-9/match.scm
index 1a2a61e..b72d005 100644
--- a/module/ice-9/match.scm
+++ b/module/ice-9/match.scm
@@ -115,6 +115,53 @@
((_ newpat m () v kt ke i)
(syntax (match-one v newpat () kt ke i))))))
+;;Bug (match '(1 2) ((and x (a ... b)) b)) fails without the following fix
+(define-syntax match-gen-ellipses
+ (syntax-rules ()
+ ((_ v p () g+s (sk ...) fk i ((id id-ls) ...))
+ (match-check-identifier p
+ ;; simplest case equivalent to (p ...), just bind the list
+ (let ((p v))
+ (if (list? p)
+ (sk ... i)
+ fk))
+ ;; simple case, match all elements of the list
+ (let loop ((ls v) (id-ls '()) ...)
+ (cond
+ ((null? ls)
+ (let ((id (reverse id-ls)) ...) (sk ... i)))
+ ((pair? ls)
+ (let ((w (car ls)))
+ (match-one w p ((car ls) (set-car! ls))
+ (match-drop-ids (loop (cdr ls) (cons id id-ls) ...))
+ fk i)))
+ (else
+ fk)))))
+ ((_ v p r g+s (sk ...) fk i ((id id-ls) ...))
+ ;; general case, trailing patterns to match, keep track of the
+ ;; remaining list length so we don't need any backtracking
+ (match-verify-no-ellipses
+ r
+ (let* ((tail-len (length 'r))
+ (ls v)
+ (len (length ls)))
+ (if (< len tail-len)
+ fk
+ (let loop ((ls ls) (n len) (id-ls '()) ...)
+ (cond
+ ((= n tail-len)
+ (let ((id (reverse id-ls)) ...)
+ (match-one ls r (#f #f) (sk ...) fk i)))
+ ((pair? ls)
+ (let ((w (car ls)))
+ (match-one w p ((car ls) (set-car! ls))
+ (match-drop-ids
+ (loop (cdr ls) (- n 1) (cons id id-ls) ...))
+ fk
+ i)))
+ (else
+ fk)))))))))
+
;;We must be able to extract vars in the new constructs!!
(define-syntax match-extract-vars
(syntax-rules (_ ___ *** ? $ = quote quasiquote and or not get! set!)
@@ -241,5 +288,5 @@
#'(begin exp ...))))))
(include-from-path/filtered
- (match-extract-vars match-two match)
- "ice-9/match.upstream.scm")
\ No newline at end of file
+ (match-gen-ellipses match-extract-vars match-two match)
+ "ice-9/match.upstream.scm")
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: new match system bug?
2010-09-04 12:38 new match system bug? Stefan Israelsson Tampe
@ 2010-09-04 12:44 ` Ludovic Courtès
2010-09-04 13:29 ` Stefan Israelsson Tampe
2010-09-04 15:02 ` Stefan Israelsson Tampe
0 siblings, 2 replies; 6+ messages in thread
From: Ludovic Courtès @ 2010-09-04 12:44 UTC (permalink / raw)
To: guile-devel
Hello!
Stefan Israelsson Tampe <stefan.tampe@spray.se> writes:
> While eating the dogfood of the new match macro I come across a bug
> e.g, this does not work!
>
> (match '(a b) ((and x (a ... b)) a))
But:
scheme@(guile-user)> (match '(a b) ((and x (a . b)) a))
$1 = a
According to the grammar in the manual, I don’t think literal ‘...’ can
be used in the middle of a list; it should only be used at the end of a
list, where it means “zero or more”:
scheme@(guile-user)> (match '(a b) ((a ...) a))
$2 = (a b)
Thanks,
Ludo’.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: new match system bug?
2010-09-04 12:44 ` Ludovic Courtès
@ 2010-09-04 13:29 ` Stefan Israelsson Tampe
2010-09-04 15:00 ` Ludovic Courtès
2010-09-04 15:02 ` Stefan Israelsson Tampe
1 sibling, 1 reply; 6+ messages in thread
From: Stefan Israelsson Tampe @ 2010-09-04 13:29 UTC (permalink / raw)
To: guile-devel
On Saturday, September 04, 2010 02:44:49 pm Ludovic Courtès wrote:
> Hello!
>
> Stefan Israelsson Tampe <stefan.tampe@spray.se> writes:
> > While eating the dogfood of the new match macro I come across a bug
> > e.g, this does not work!
> >
> > (match '(a b) ((and x (a ... b)) a))
>
> But:
>
> scheme@(guile-user)> (match '(a b) ((and x (a . b)) a))
> $1 = a
>
> According to the grammar in the manual, I don’t think literal ‘...’ can
> be used in the middle of a list; it should only be used at the end of a
> list, where it means “zero or more”:
>
> scheme@(guile-user)> (match '(a b) ((a ...) a))
> $2 = (a b)
>
> Thanks,
> Ludo’.
How true, It's just that the code we took has an extension with a Bug in it.
It was intended to work for that case as well.
From match.upstream.scm:
;; 2007/07/21 - allowing ellipse patterns in non-final list positions
They just stopped variants of
the form (a ... b ...) cause it led to higher order matchers that could be
avoided by another means me thinks.
So either.
1. we allow for this extension. or
2. Add a nice error message explaining that that feature is not suported.
Right now - this is a Bug :-)
Note. I would like to allow multiple a ... patterns but warn against it use
and change the algorithm. The reason is that there exists a common pattern
idiom. Namely ( a a a a - b b b b b - c c c c c) e.g. using separators.
essentially it is very kind to allow people to do:
(match list ((x ... '- . l) (begin (handle x) (f l))))
So you essentially allow a anti gready ... operator. Note here that using <x>
abstractions althogh it works for the above example, it cannot reproduce a non
gready operator. For that you would need the continuation inside the match
abstractions.
Cheers
Stefan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: new match system bug?
2010-09-04 13:29 ` Stefan Israelsson Tampe
@ 2010-09-04 15:00 ` Ludovic Courtès
2010-09-04 15:17 ` Stefan Israelsson Tampe
0 siblings, 1 reply; 6+ messages in thread
From: Ludovic Courtès @ 2010-09-04 15:00 UTC (permalink / raw)
To: guile-devel
Hi Stefan!
Stefan Israelsson Tampe <stefan.tampe@spray.se> writes:
> How true, It's just that the code we took has an extension with a Bug in it.
> It was intended to work for that case as well.
>
> From match.upstream.scm:
> ;; 2007/07/21 - allowing ellipse patterns in non-final list positions
Then how about reporting it upstream Cc: guile-devel? :-)
Thanks,
Ludo’.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: new match system bug?
2010-09-04 15:00 ` Ludovic Courtès
@ 2010-09-04 15:17 ` Stefan Israelsson Tampe
0 siblings, 0 replies; 6+ messages in thread
From: Stefan Israelsson Tampe @ 2010-09-04 15:17 UTC (permalink / raw)
To: guile-devel
On Saturday, September 04, 2010 05:00:31 pm Ludovic Courtès wrote:
> Hi Stefan!
>
> Stefan Israelsson Tampe <stefan.tampe@spray.se> writes:
> > How true, It's just that the code we took has an extension with a Bug in
> > it. It was intended to work for that case as well.
> >
> > From match.upstream.scm:
> > ;; 2007/07/21 - allowing ellipse patterns in non-final list positions
>
> Then how about reporting it upstream Cc: guile-devel? :-)
>
> Thanks,
> Ludo’.
I'll have a chat with the people at #scheme
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: new match system bug?
2010-09-04 12:44 ` Ludovic Courtès
2010-09-04 13:29 ` Stefan Israelsson Tampe
@ 2010-09-04 15:02 ` Stefan Israelsson Tampe
1 sibling, 0 replies; 6+ messages in thread
From: Stefan Israelsson Tampe @ 2010-09-04 15:02 UTC (permalink / raw)
To: guile-devel
[-- Attachment #1: Type: Text/Plain, Size: 770 bytes --]
On Saturday, September 04, 2010 02:44:49 pm Ludovic Courtès wrote:
> Hello!
>
> Stefan Israelsson Tampe <stefan.tampe@spray.se> writes:
> > While eating the dogfood of the new match macro I come across a bug
> > e.g, this does not work!
> >
> > (match '(a b) ((and x (a ... b)) a))
>
> But:
>
> scheme@(guile-user)> (match '(a b) ((and x (a . b)) a))
> $1 = a
>
> According to the grammar in the manual, I don’t think literal ‘...’ can
> be used in the middle of a list; it should only be used at the end of a
> list, where it means “zero or more”:
>
> scheme@(guile-user)> (match '(a b) ((a ...) a))
> $2 = (a b)
>
> Thanks,
> Ludo’.
I Included a trailing pattern error message to match.scm in this patch.
/Stefan
[-- Attachment #2: match-trailing.patch --]
[-- Type: text/x-patch, Size: 1808 bytes --]
diff --git a/module/ice-9/match.scm b/module/ice-9/match.scm
index 1a2a61e..3a709a1 100644
--- a/module/ice-9/match.scm
+++ b/module/ice-9/match.scm
@@ -115,6 +115,36 @@
((_ newpat m () v kt ke i)
(syntax (match-one v newpat () kt ke i))))))
+;;error messag added
+(define-syntax match-gen-ellipses
+ (syntax-rules ()
+ ((_ v p () g+s (sk ...) fk i ((id id-ls) ...))
+ (match-check-identifier p
+ ;; simplest case equivalent to (p ...), just bind the list
+ (let ((p v))
+ (if (list? p)
+ (sk ... i)
+ fk))
+ ;; simple case, match all elements of the list
+ (let loop ((ls v) (id-ls '()) ...)
+ (cond
+ ((null? ls)
+ (let ((id (reverse id-ls)) ...) (sk ... i)))
+ ((pair? ls)
+ (let ((w (car ls)))
+ (match-one w p ((car ls) (set-car! ls))
+ (match-drop-ids (loop (cdr ls) (cons id id-ls) ...))
+ fk i)))
+ (else
+ fk)))))
+ ((_ v p r g+s (sk ...) fk i ((id id-ls) ...))
+ ;; general case, trailing patterns to match, keep track of the
+ ;; remaining list length so we don't need any backtracking
+ (match-verify-no-ellipses
+ r
+ (match-syntax-error
+ "trailing pattern to ... , eg. (x ... y) is not supported")))))
+
;;We must be able to extract vars in the new constructs!!
(define-syntax match-extract-vars
(syntax-rules (_ ___ *** ? $ = quote quasiquote and or not get! set!)
@@ -241,5 +271,5 @@
#'(begin exp ...))))))
(include-from-path/filtered
- (match-extract-vars match-two match)
- "ice-9/match.upstream.scm")
\ No newline at end of file
+ (match-gen-ellipses match-extract-vars match-two match)
+ "ice-9/match.upstream.scm")
^ permalink raw reply related [flat|nested] 6+ messages in thread
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2010-09-04 12:38 new match system bug? Stefan Israelsson Tampe
2010-09-04 12:44 ` Ludovic Courtès
2010-09-04 13:29 ` Stefan Israelsson Tampe
2010-09-04 15:00 ` Ludovic Courtès
2010-09-04 15:17 ` Stefan Israelsson Tampe
2010-09-04 15:02 ` Stefan Israelsson Tampe
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