[Haskell-cafe] A functor for two Peano systems

[Galaxy Being]

That must be my problem. Thanks for the info.

On Mon, Apr 5, 2021 at 12:36 PM Tom Ellis <
tom-lists-haskell-cafe-2017 at jaguarpaw.co.uk> wrote:

> On Mon, Apr 05, 2021 at 12:17:23AM -0500, Galaxy Being wrote:
> > I'm just not understanding the concept of a functor in this context: I
> have
> > this
> [...]
> > It seems there should be just one plus, function that would handle both
> an
> > Int-based Peano and the MyNum-based Peano, not two. But in this
> definition
> >
> > fmap :: (a -> b) -> f a -> f b
> >
> > The (a -> b) should be "lifted" over the f a -> f b But I can't conceive
> of
> > how this should all fit together
>
> Are you perhaps confusing the ML notion of "functor" with the Haskell
> notion of "Functor" (which is just a particular typeclass)?
>
> In fact, Haskell's type classes as a whole are probably closer to ML's
> "functors" than Haskell's "Functor"s are!
>
> Tom
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