Re: [Haskell-cafe] Category Theory and Haskell

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Gytis Žilinskas writes:

How difficult would it be to study category theory and simultaneously come up with Haskell examples of various results that it presents?

There are some aspects of CT that you will not be able to express in Haskell easily (try encoding the forgetful functor, for instance). But there are other things which translate quite nicely. As one example, I've been using Haskell to explore the connection between adjunctions and monads, and have found it quite rewarding. My efforts so far are here: https://github.com/jwiegley/posts/blob/master/Adjunctions%20in%20Haskell/Adj... What I found most compelling from that code is I only need a minimal definition of the Prod ⊣ Hom adjunction, (ε and η -- and their definitions are trivial), I get all the behavior of the well-known State monad, whose typical implementation via >>= is rather tricky. Doing this exploration in Haskell -- with the aid of the type-checker -- made certain connections clear that were difficult to see in the abstract. And it was plenty of fun besides. :) Happy brain spelunking, -- John Wiegley FP Complete Haskell tools, training and consulting http://fpcomplete.com johnw on #haskell/irc.freenode.net