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")