Initial data commit

Task/Queue-Definition/Racket/queue-definition-1.rkt

@@ -0,0 +1,22 @@
+#lang racket
+
+(define (make-queue) (mcons #f #f))
+(define (push! q x)
+  (define new (mcons x #f))
+  (if (mcar q) (set-mcdr! (mcdr q) new) (set-mcar! q new))
+  (set-mcdr! q new))
+(define (pop! q)
+  (define old (mcar q))
+  (cond [(eq? old (mcdr q)) (set-mcar! q #f) (set-mcdr! q #f)]
+        [else (set-mcar! q (mcdr old))])
+  (mcar old))
+(define (empty? q)
+  (not (mcar q)))
+
+(define Q (make-queue))
+(empty? Q) ; -> #t
+(push! Q 'x)
+(empty? Q) ; -> #f
+(for ([x 3]) (push! Q x))
+(pop! Q)   ; -> 'x
+(list (pop! Q) (pop! Q) (pop! Q)) ; -> '(0 1 2)