[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?
Cheers
Ben
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