langs a-z

Task/Hailstone-sequence/TXR/hailstone-sequence.txr

@@ -0,0 +1,26 @@
+@(do (defun hailstone (n)
+       (cons n
+             (gen (not (eq n 1))
+                  (set n (if (evenp n)
+                           (trunc n 2)
+                           (+ (* 3 n) 1)))))))
+@(next :list @(mapcar* (fun tostring) (hailstone 27)))
+27
+82
+41
+124
+@(skip)
+8
+4
+2
+1
+@(eof)
+@(do (let ((max 0) maxi)
+       (each* ((i (range 1 99999))
+               (h (mapcar* (fun hailstone) i))
+               (len (mapcar* (fun length) h)))
+         (if (> len max)
+           (progn
+             (set max len)
+             (set maxi i))))
+       (format t "longest sequence is ~a for n = ~a\n" max maxi)))