CODEWITHSUNDEEP
haskell
RussAbbott
RussAbbott

Reputation: 2738

Is it possible to have functions with multiple type signatures in Haskell

I apologize for this question. I've been away for a while and feel like I've forgotten everything I knew.

I want to do something like this.

data X = X 
data Y = Y

myEq X X = True
myEq Y Y = True
myEq _ _ = False

I've tried various declarations for myEq. I've also tried to define a type class that might do it. But nothing I could think of compiled.

Is something like this possible? And if so, how?

Thanks.

Upvotes: 0

Views: 127

Answers (1)

RussAbbott
RussAbbott

Reputation: 2738

I think this will do it.

data X = X deriving (Show)
data Y = Y deriving (Show)

class (Show a) => MyEquatable a 

instance MyEquatable X
instance MyEquatable Y

myEq :: (MyEquatable a, MyEquatable b) => a -> b -> Bool
myEq a b = show a == show b

Of course, if doesn't have to be show, but that's a simple way to do it.

Upvotes: 1

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