[Haskell-beginners] Why the compiler does not commit to a type class?
jasonsychau at gmail.com
Fri Apr 17 20:00:28 UTC 2020
Yes - if you look at the number types, you will find different number types and not integer types are providing support that’s not in Integer, so compiler is giving safest assumption.
Sent from my iPhone
> On Apr 17, 2020, at 12:56 PM, Alexander Chen <alexander at chenjia.nl> wrote:
> Prelude> u = undefined
> Prelude> k :: (Ord a, Num b) => a -> b -> a; k = u
> Prelude> :t k 1 2
> k 1 2 :: (Ord a, Num a) => a
> Prelude> :t k (1 :: Integer) 2
> k (1 :: Integer) 2 :: Integer
> In the first version the compiler is not really pushed so it simply gives back the type class constriction it has to adhere to. While in the second it is pushed to give an more specific answer and thus the :: Integer.
> Is this train of thought correct?
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