[Haskell-beginners] A Quantity Type - Integer without the Negative #'s

[Daniel Carrera]

That's an interesting question. I would like to see the answer too. I 
can think of a completely impractical way to do it:

data Quantity = 0 | 1 | 2 | 3 | ... | 65532


But of course, listing every integer seems like a dumb solution. But 
this gives me more confidence that there is a smart solution to your 
problem and we just need to find it.

Daniel.



aditya siram wrote:
> Hi all,
> Is there a datatype in Haskell that can be used to represent only 
> quantities >= 0?  I got bitten by a bug because I forgot to reject an 
> amount that was below zero after applying a decrementing operator. A 
> simple unit test would have caught this, but I was wondering if there 
> was some way of getting the type system to ensure this.
> 
> thanks ...
> -deech
> 
> 
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