On Saturday, September 04, 2010 02:44:49 pm Ludovic Courtès wrote:
> Hello!
>
> Stefan Israelsson Tampe <stefan.ta...@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
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")
