(*
A happy number is defined by the following process. Starting with any positive integer, replace the number
by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will
stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends
 in 1 are happy numbers, while those that do not end in 1 are unhappy numbers. Display an example of your
output here.
*)

local
	fun get_digits
			(d, s) where (d = 0) = s
		| 	(d, s) = get_digits( d div 10, (d mod 10) :: s)
		| 	n = get_digits( n div 10, [n mod 10] )
	;
	fun mem
			(x, []) = false
		| 	(x, a :: as) where (x = a) = true
		| 	(x, _ :: as) = mem (x, as)
in
	fun happy
			1 = "happy"
		|	n =
				let
					val this = (fold (+,0) ` map (fn n = n ^ 2) ` get_digits n);
					val sads = [2, 4, 16, 37, 58, 89, 145, 42, 20]
				in
					if (mem (n,sads)) then
						"unhappy"
					else
						happy this
				end
end
;

foreach (fn n = (print n; print " is "; println ` happy n)) ` iota 10;