26 lines
757 B
Scheme
26 lines
757 B
Scheme
#lang scheme/base
|
|
|
|
(require (for-template (only-in scheme/base ...)))
|
|
|
|
(provide check-pat-ellipses)
|
|
|
|
(define ((check-pat-ellipses orig-stx) stx)
|
|
(let loop ([stx stx][car-ok? #f])
|
|
(cond
|
|
[(syntax? stx) (loop (syntax-e stx) car-ok?)]
|
|
[(pair? stx)
|
|
(if (and (not car-ok?)
|
|
(identifier? (car stx))
|
|
(free-identifier=? (car stx) (quote-syntax ...)))
|
|
(raise-syntax-error #f
|
|
"ellipsis without preceding form"
|
|
orig-stx
|
|
(car stx))
|
|
(begin (loop (car stx) #f)
|
|
(loop (cdr stx) #t)))]
|
|
[(vector? stx)
|
|
(for-each (lambda (stx) (loop stx #f)) (vector->list stx))]
|
|
[else (void)])))
|
|
|
|
|