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16-macros/main.rkt

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+#lang pl
+
+(define-type Token = (U Symbol Integer))
+
+(: in? : Symbol (Listof Symbol) -> Boolean)
+(define (in? s l) (and (not (null? l)) (not (and (not (symbol=? s (first l))) (not (in? s (rest l)))))))
+
+(test (in? 'a '(b d e a f e)))
+(test (in? 'a '(b x e a x e)))
+(test (in? 'a '(a b d e a f e)))
+(test (in? 'a '(b d e a f e a)))
+(test (not (in? 'a '(b d e f e))))
+(test (not (in? 'a '())))
+
+#|
+(: abc : String -> Boolean)
+; Identifies strings that match "(ab(c+))+"
+(define abc (automaton one (four)
+                       [one : (a -> two)]
+                       [two : (b -> three)]
+                       [three : (c -> four)]
+                       [four : (c -> four) (a -> two)]))
+
+(test (abc "abccc"))
+(test (abc "abcccabc"))
+(test (not (abc "ab")))
+(test (not (abc "q")))
+(test (not (abc "abcb")))
+(test (not (abc "abcab")))
+|#