[Haskell-cafe] Haskell function composition commutivity?

[Galaxy Being]

Your answers seem to originate outside of normal Haskell tutorials. Where
can I start with this higher superset theory?

On Tue, Apr 13, 2021 at 1:19 PM Viktor Dukhovni <ietf-dane at dukhovni.org>
wrote:

> > 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)
>
> --
>         Viktor.
>
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