Re: [Haskell-beginners] (Integral a) => a vs Integer

On Tue, Jul 12, 2011 at 7:20 PM, Dan Ross wrote:

Hi all-

I'm going through Learn You a Haskell for Great Good and I don't understand the advantage of using (Integral a)=> a vs just Integer as I show below.

Could someone explain this to me?

Thanks,

Dan

lucky :: (Integral a) => a -> String lucky 7 = "LUCKY NUMBER SEVEN!" lucky x = "Sorry, you're out of luck, pal!"

lucky :: Integer -> String lucky 7 = "LUCKY NUMBER SEVEN!" lucky x = "Sorry, you're out of luck, pal!"

Hi Dan, The first version is polymorphic, and will work on *any* instance of Integral. This would allow people to use Int, Int32, Int64, etc. The second version requires the user to pass in specifically an Integer. Michael