#lang racket
+(define (memq item x)
+ (cond ((null? x) #f)
+ ((eq? item (car x)) x)
+ (else (memq item (cdr x)))))
+
;; leaf nodes
(define (make-leaf leaf weight)
(list 'leaf leaf weight))
(cadr pair))
(make-leaf-set (cdr pairs))))))
-(provide make-code-tree make-leaf decode leaf? symbol-leaf left-branch right-branch symbols)
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+(provide make-code-tree
+ make-leaf
+ decode
+ leaf?
+ symbol-leaf
+ left-branch
+ right-branch
+ symbols
+ make-leaf-set
+ adjoin-set)
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