[Haskell-beginners] Enum for natural numbers

[Deniz Dogan]

2009/12/17  <kane96 at gmx.de>:
> Hi,
> I have data Nat = Z | S Nat deriving (Eq,Ord,Show)
>
> toEnum should return Z for negative numbers. I did something like this but the problem is I don't know how to set "less than". I tried > and lt:
>
> instance Enum Nat where
>    toEnum (gt 0) = S Z
>    toEnum (lt 1) = Z
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Fill in the gaps:

instance Enum Nat where
    toEnum x | x <= 0 = ...
             | otherwise = ...

-- 
Deniz Dogan