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16-macros/17.rkt

@@ -0,0 +1,40 @@
+#lang racket
+
+
+
+(define-syntax let*
+  (syntax-rules () ;; special tokens
+    [(let* () body ...)
+     (let () body ...)]
+    [(let* ((x v) (xs vs) ...) body ...)
+     (let ((x v)) (let* ((xs vs) ...) body ...))]))
+
+
+
+(let* [(x 5)
+       (y (+ x 2))]
+  y)
+;; ->
+(let ((x 5))
+  (let* ((y (+ x 2)))
+    y))
+;; ->
+(let ((x 5))
+  (let ((y (+ x 2)))
+    (let* ()
+      y)))
+;; ->
+(let ((x 5))
+  (let ((y (+ x 2)))
+    (let ()
+      y)))
+
+(define-syntax annd
+  (syntax-rules ()
+    [(annd) #t]
+    [(annd x) (if x x #f)]
+    [(annd x y ...) (if x (annd y ...) #f)]))
+
+(annd #f (/ 5 0))
+(and 5 2 3)
+(annd 5 2 3)

16-macros/main.rkt

@@ -0,0 +1,30 @@
+#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")))
+|#