A-M baby

Task/Happy-numbers/APL/happy-numbers.apl

@@ -0,0 +1,20 @@
+     ∇ HappyNumbers arg;⎕IO;∆roof;∆first;bin;iroof
+[1]   ⍝0: Happy number
+[2]   ⍝1: http://rosettacode.org/wiki/Happy_numbers
+[3]    ⎕IO←1                              ⍝ Index origin
+[4]    ∆roof ∆first←2↑arg,10              ⍝
+[5]
+[6]    bin←{
+[7]        ⍺←⍬                            ⍝ Default left arg
+[8]        ⍵=1:1                          ⍝ Always happy!
+[9]
+[10]       numbers←⍎¨1⊂⍕⍵                 ⍝ Split numbers into parts
+[11]       next←+/{⍵*2}¨numbers           ⍝ Sum and square of numbers
+[12]
+[13]       next∊⍺:0                       ⍝ Return 0, if already exists
+[14]       (⍺,next)∇ next                 ⍝ Check next number (recursive)
+[15]
+[16]   }¨iroof←⍳∆roof                     ⍝ Does all numbers upto ∆root smiles?
+[17]
+[18]   ⎕←~∘0¨∆first↑bin/iroof             ⍝ Show ∆first numbers, but not 0
+     ∇