[Haskell-cafe] Relevance and applicability of category theory

Gabor Greif gabor at mac.com
Thu Jan 31 17:29:12 EST 2008

Am 31.01.2008 um 18:13 schrieb Dan Weston:

> Even though you cannot "dive into this matter now", maybe when you  
> get time you can update your blog with an explicit embedding of  
> Haskell monads and arrows in your Thrist construction. Concrete  
> examples will help me (and probably others) more quickly see the  
> novelty, increased generality, and usefulness of a Thrist.

Okay, I took my time and came up with:


Comments welcome.

> Also, although you say that thrists are the moral equivalent of a  
> free category, it appears (at least to me) possible that the first  
> Thrist argument enables the construction of a restricted domain  
> monad, e.g. (Eq a => Set a) monad. Is this so?

Hmmm, not sure what you asking for. If you have a monad instance Set  
a that has Eq a attached, this
already would do what you want, no? An example would help me to  

> Dan




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