Data commit

Task/First-class-environments/Racket/first-class-environments.rkt

@@ -0,0 +1,28 @@
+#lang racket
+
+(define namespaces
+  (for/list ([i (in-range 1 13)])
+    (define ns (make-base-namespace))
+    (eval `(begin (define N ,i) (define count 0)) ns)
+    ns))
+
+(define (get-var-values name)
+  (map (curry namespace-variable-value name #t #f) namespaces))
+
+(define code
+  '(when (> N 1)
+     (set! N (if (even? N) (/ N 2) (+ 1 (* N 3))))
+     (set! count (add1 count))))
+
+(define (show-nums nums)
+  (for ([n nums]) (display (~a n #:width 4 #:align 'right)))
+  (newline))
+
+(let loop ()
+  (define Ns (get-var-values 'N))
+  (show-nums Ns)
+  (unless (andmap (λ(n) (= n 1)) Ns)
+    (for ([ns namespaces]) (eval code ns))
+    (loop)))
+(displayln (make-string (* 4 12) #\=))
+(show-nums (get-var-values 'count))