Data commit

Task/Ackermann-function/Scheme/ackermann-function-1.ss

@@ -0,0 +1,5 @@
+(define (A m n)
+    (cond
+        ((= m 0) (+ n 1))
+        ((= n 0) (A (- m 1) 1))
+        (else (A (- m 1) (A m (- n 1))))))

Task/Ackermann-function/Scheme/ackermann-function-2.ss

@@ -0,0 +1,29 @@
+(define (A m n)
+  (letrec ((A-stream
+    (cons-stream
+      (ints-from 1) ;; m = 0
+      (cons-stream
+        (ints-from 2) ;; m = 1
+        (cons-stream
+          ;; m = 2
+          (stream-map (lambda (n)
+                        (1+ (* 2 (1+ n))))
+                      (ints-from 0))
+          (cons-stream
+            ;; m = 3
+            (stream-map (lambda (n)
+                          (- (knuth-up-arrow 2 (- m 2) (+ n 3)) 3))
+                        (ints-from 0))
+             ;; m = 4...
+            (stream-tail A-stream 3)))))))
+    (stream-ref (stream-ref A-stream m) n)))
+
+(define (ints-from n)
+  (letrec ((ints-rec (cons-stream n (stream-map 1+ ints-rec))))
+    ints-rec))
+
+(define (knuth-up-arrow a n b)
+  (let loop ((n n) (b b))
+    (cond ((= b 0) 1)
+          ((= n 1) (expt a b))
+          (else    (loop (-1+ n) (loop n (-1+ b)))))))