[Haskell-cafe] Pointless functors

Jonathan Cast jonathanccast at fastmail.fm
Fri Mar 13 12:12:56 EDT 2009

On Sat, 2009-03-14 at 02:12 +1000, Matthew Brecknell wrote:
> Ross Paterson wrote: 
> > No.  Choose an arbitrary element shape :: f () and define
> >        point x = fmap (const x) shape
> Interesting. Is the arbitrariness of the shape some sort of evidence
> that Pointed is not really a very useful class in its own right?

A simpler bit of evidence is that the only law I can think of for point
(in its own right) is

  fmap f . point = point . f

which we get free anyway.


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