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16-macros/17.rkt

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+#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)