[Haskell-cafe] Article review: Category Theory

Brian Hulley brianh at metamilk.com
Wed Jan 17 09:27:45 EST 2007

David House wrote:
> http://en.wikibooks.org/wiki/Haskell/Category_theory
> I'd love comments from newcomers and experts alike regarding my
> approach, the content, improvements and so on. Of course, it's on the
> wikibook, so if you have anything to add (that's not _too_ substantial
> otherwise I'd recommend discussion first) then go ahead.

Hi David,

In the introduction you say that Set is the category of all sets with 
morphisms as standard functions and composition as standard function 

But in the second exercise in the intro it's clear that function composition 
is not associative. Therefore surely this means everything based on function 
composition can't be a category?

Also, why does this exercise contain redundant morphisms (I hope I'm not 
spoiling it for anyone by saying this or perhaps I've just totally 
misunderstood everything)?

Thanks, Brian.

More information about the Haskell-Cafe mailing list