September 2017 Update

Task/Happy-numbers/8th/happy-numbers.8th

@@ -0,0 +1,29 @@
+: until!  "not while!" eval i;
+
+with: w
+with: n
+
+: sumsqd  \ n -- n
+    0 swap repeat
+        0; 10 /mod -rot sqr + swap
+    again ;
+
+: cycle \ n xt -- n
+    >r
+    dup r@ exec  \ -- tortoise, hare
+    repeat
+        swap r@ exec
+        swap r@ exec r@ exec
+    2dup = until!
+    rdrop drop ;
+
+: happy?  ' sumsqd cycle 1 = ;
+
+: .happy \ n --
+    1 repeat
+        dup happy? if  dup . space  swap 1- swap  then 1+
+    over 0 > while!
+    2drop cr ;
+
+;with
+;with