Re: [Haskell-cafe] Why is Bool no instance of Num and Bits?

Nope, it's in the Haskell standard. It means we can type: 1 + (2 :: Int) and have it work Otherwise what type would 1 have? Integer? Float? It's just a way of giving constants the type :: Num a => a On Fri, May 8, 2009 at 4:53 PM, Andrew Wagner wrote:

Hmm, I never knew that. Is that a GHC thing? Is it strictly necessary? Seems like it could be done in the Num instance for Integers, Ints, etc.

On Fri, May 8, 2009 at 11:51 AM, Neil Mitchell wrote:

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Err, I'm not seeing the danger of this (+) :: forall a. (Num a) => a -> a -> a Doesn't this require the two parameters to be the same instance of Num?

I didn't at first, then I remembered:

1 + True = fromInteger 1 + True

And if we have Num for Bool, it type checks.

Thanks

Neil