curly tests

brag/examples/curly-quantifier.rkt

@@ -1,7 +1,8 @@
 #lang brag
 ;; test the curly quantifier
-start : a-rule | b-rule | c-rule | d-rule
+start : a-rule | b-rule | c-rule | d-rule | e-rule
 a-rule : "a"{2} ; exactly 2
 b-rule : "b"{,2} ; up to 2
 c-rule : "c"{2,} ; 2 or more
 d-rule : "d"{2,3} ; 2 or 3
+e-rule : "e"{} ; 0 or more

brag/test/test-curly-quantifier.rkt

@@ -21,3 +21,8 @@
 (check-equal? (parse-to-datum "dd") '(start (d-rule "d" "d")))
 (check-equal? (parse-to-datum "ddd") '(start (d-rule "d" "d" "d")))
 (check-exn exn:fail:parsing? (λ () (parse-to-datum "dddd")))
+
+(check-equal? (syntax->datum ((make-rule-parser e-rule) "")) '(e-rule)) ; to prevent ambiguity with b-rule while parsing empty string
+(check-equal? (parse-to-datum "e") '(start (e-rule "e")))
+(check-equal? (parse-to-datum "ee") '(start (e-rule "e" "e")))
+(check-equal? (parse-to-datum "eee") '(start (e-rule "e" "e" "e")))