[Haskell-beginners] Further constraining types

[David Virebayre]

2011/8/5 Arlen Cuss <celtic at sairyx.org>:
>> I would go with :
>>  validatePositive :: Int -> Maybe (Positive Int)
>>  square :: Positive Int -> Positive Int
>
> But squaring a negative Int is still guaranteed to be positive!

I thought he said he wanted to work with natural numbers.

David.