What's a good example for a Haskell functor that is not an applied functor?
Learning functors in Haskell for example. [Integer]
or [] Integer
, I understand that the functor needs to be defined fmap
(in the list example:) fmap = map
. If I get it right, the functor can implement a sequential application <*>
to become an applied functor. That's why
[(1+), (2+)]
is a wonderful item in the list of instances [] Integer
. And an expression like
(+) <$> [1..10] <*> [101..110]
has the meaning.
The instance examples Functor
I found were also applicative functors. That is, there was a reasonable definition <*>
. Typical examples for functors. Perhaps [] or e, Tree, e →, Pair, (,) e, ... are also applicative (ie, there is a reasonable definition <*>
). From what I understand, they are all monads, even!
I found ZipList
as an example an applicative functor that is not a monad ( for some reason ).
Now there is a functor that is not an applied functor and sanely?
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