[Haskell-cafe] Relevance and applicability of category theory
gabor at mac.com
Thu Jan 31 04:14:20 EST 2008
Am 31.01.2008 um 01:23 schrieb aaltman at pdx.edu:
> 3. I believe the documentation stating that Haskell arrows are a
> generalization of Haskell monads, but arrows are a categorical
> thing too and in that context bear a much more distant relationship
> to monads. Does a Haskell arrow have Hask as domain and codomain?
> Or is one particular element in Hask its domain and possibly
> another its codomain? Those are not at all the same thing.
Without being able to dive into this matter now,
I just want to say that both the Haskell monads
and arrows can be generalized to something
I call a "thrist", which appears to be the moral
equivalent of a free category. The underlying
category is obtained by a two-parameter GADT
(defining the morphisms) and the domains and
codomains of its members (which are Haskell types)
being the objects.
Here is my blog entry that motivates the concept
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