[Haskell-cafe] classes question

Ross Mellgren rmm-haskell at z.odi.ac
Mon Nov 9 13:47:41 EST 2009


You did not specify what type of number it is -- in Haskell numeric  
constants like "1" are actually typed as forall a. Num a -- that is,  
can be any type of Num.

Try: plus (2::Int) 3

-Ross

On Nov 9, 2009, at 1:44 PM, Paul Tokarev wrote:

>
> Hi.
>
> I am using Hugs 98
> I have that piece of code:
>
> class PlusTimes a where
>   plus :: a -> a -> a
>
> instance PlusTimes Int where
>   plus x y = x + y
>
> when I run : "plus 2 3" I get this error:
> ERROR - Unresolved overloading
> *** Type       : (Num a, PlusTimes a) => a
> *** Expression : plus 2 3
>
> What am I doing wrong?
> Thanks.
>
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