Re: A question about overloading

Hi Rudolf,

In this case you should be able to use generic equality:

importStdEnv
importData.GenEq
::Enum =A |B |C
instance ==Enum derive gEq
derivegEq Enum

If you want to handle certain cases non-generically you can use:

instance ==Enum
where
(==) A A =False
(==) s1s2=s1===s2

Kind regards,
Gijs Alberts

On 10/3/22 19:58, Rudolf Meijer via clean-list wrote:
> I need to compare two values of an "enumeration type" for equality. 
> Say the type definition is :: Enum =  A | B | C. The only way I have 
> found to overload == on this type is the following:
>
> instance == Enum
> where
>     (==) s1 s2 = case (s1, s2) of
>         (A, A) = True
>         (B, B) = True
>         (C, C) = True
>         otherwise = False
>
> Although this works (I have checked), it does seem clumsy and will get 
> less workable when the enumeration type has quite a few values more. 
> Who has a better idea?
>
> Thanks again in advance.
> Rudolf Meijer
>
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