[Haskell-cafe] Re: Re: Re: Full strict functor by abusing Haskell exceptions

Ben Franksen ben.franksen at online.de
Fri Sep 17 16:39:04 EDT 2010

Román González wrote:
> On Thu, Sep 16, 2010 at 2:12 PM, Ben Franksen
> <ben.franksen at online.de>wrote:
>> Sjoerd Visscher wrote:
>> > But StrictIncl can't be a pointed functor, only endofunctors can be
>> > pointed.
>> Could someone tell me what exactly a pointed functor is? I googled but
>> did not find a definition.
> Here you will find what a Pointed Functor would be =>
> http://haskell.org/sitewiki/images/8/85/TMR-Issue13.pdf
> Look up for the Typeclassopedia, start reading functor, next thing you
> will find is the Pointed typeclass

Thanks for the link. What I actually wanted was a mathematical definition,
though. From the TMR article I gather that a pointed functor could be
defined as an endo-functor

  F: C -> C

together with a natural transformation

  pure: Id -> F

where Id: C -> C is the identity functor.

No additional laws (beside naturality of pure) are imposed.

Right so far?

Why is this an interesting structure?


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