[Haskell-cafe] Haskell function composition commutivity?
ietf-dane at dukhovni.org
Tue Apr 13 18:14:48 UTC 2021
> On Apr 13, 2021, at 2:02 PM, Tom Smeding <x at tomsmeding.com> wrote:
> Although, because of the fact that you omitted 'Functor f =>' and
> instead chose to write the constraint in prose beforehand, I get the
> feeling that you may be speaking mathematically, not about Haskell as
> compiled by GHC.
Yes, mathematically, with Haskell-like syntax. Also the
functors in question were intended to stand for specific
functors, rather than be universally quantified.
So perhaps better:
Yoneda (with A some type and F some functor):
foo :: forall b. (A -> b) -> F b
<=> foo bar = fmap bar (foo (id @A)
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