CODEWITHSUNDEEP
haskell
Sarah Xoxo
Sarah Xoxo

Reputation: 115

How to declare multiple instances for the same type?

I have the following instance:

instance Show ZZ where
   show zz = toHexa (zzToInt zz)

I need another instance of Show for the type ZZ like 

instance Show ZZ where
   show zz = ...

How can I solve this problem? I need to declare the second Show in another way.

Upvotes: 1

Views: 317

Answers (1)

chepner
chepner

Reputation: 530823

You can only have one instance per type. If you need (or rather, want) another one, you need to define a new type.

newtype ZZOther = ZZOther ZZ

instance Show ZZOther where
    show (ZZOther zz) = ... -- do something with zz :: ZZ

Upvotes: 7

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