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

Precisely. On Tue, Jul 12, 2011 at 7:44 PM, Dan Ross wrote:

Ah. Because Integer is an instance of Integral right?

So using Integer would be more restrictive.

On Tue, 12 Jul 2011 19:22:36 +0300, Michael Snoyman wrote:

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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