allow optional specifcation of var pattern

original commit: b8777d20b26837d8ecfa78eeeda25fdccdb4a783
This commit is contained in:
Sam Tobin-Hochstadt 2010-06-21 17:37:47 -04:00
parent e73d9f5ee8
commit 84247a1882

View File

@ -58,8 +58,8 @@
(define-match-expander Listof:
(lambda (stx)
(syntax-parse stx
[(_ elem-pat)
#'(Mu: var (Union: (list (Value: '()) (Pair: elem-pat (F: var)))))])))
[(_ elem-pat (~optional var-pat #:defaults ([var-pat #'var])))
(syntax/loc stx (Mu: var-pat (Union: (list (Value: '()) (Pair: elem-pat (F: var-pat))))))])))
(define-match-expander List:
(lambda (stx)