Standard ML of New Jersey Programming question (no iterators can be used, only recursion)

1. An integer is said to be square-free if it is not divisible by any perfect square other than 1. Write a function sqfree that checks whether an integer is square-free. You may assume that 0 is square-free.

   You may define auxiliary functions. For instance,

    - sqfree; val it = fn : int -> bool - sqfree 10; val it = true : bool - sqfree 75; val it = false : bool - sqfree 63; val it = false : bool - sqfree ~123454321; val it = false : bool