I'm trying to implement fmap for functions and can't quite figure out how to the "lift" applies to a function as compared to how all the documentation refers to simple kinds like Maybe
The type of the function I want to implement is
fmapFunction :: (a -> b) -> (e -> a) -> (e -> b)
Any ideas how I should go about this?
It may be easier to see if you flip the types around:
(e -> a) -> (a -> b) -> (e -> b)
We can turn an e
into an a
, and an a
into a b
. So how can we turn an e
into a b
?
Don't focus too much on "lifting"; with Functor
instances, the best way to discover the implementation is simply to follow the type.
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