A-M baby

Task/Hailstone-sequence/ACL2/hailstone-sequence.acl2

@@ -0,0 +1,16 @@
+(defun hailstone (len)
+    (loop for x = len
+             then (if (evenp x)
+                         (/ x 2)
+                         (+ 1 (* 3 x)))
+        collect x until (= x 1)))
+
+;; Must be tail recursive
+(defun max-hailstone-start (limit mx curr)
+   (declare (xargs :mode :program))
+   (if (zp limit)
+       (mv mx curr)
+       (let ((new-mx (len (hailstone limit))))
+          (if (> new-mx mx)
+              (max-hailstone-start (1- limit) new-mx limit)
+              (max-hailstone-start (1- limit) mx curr)))))