Re: Free monads

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Andres Löh writes:

I'll follow Simon's lead, and ask a similar question with a similar motivation. I'm going to talk about free monads at the upcoming Haskell eXchange next Wednesday. I'll not limit myself to a particular library, and I'm open to related approaches (e.g. "operational") as well.

One way I think about is: for the same reason you might want to pass around a list of numbers, rather than a sum or a length -- i.e., so that consume those numbers in multiple, different ways -- so too you might want to pass a list of "effects" (do this, do this, then do that) rather than a single, composite effect. In this sense, the free monad is just a free monoid in the category of endofunctors, and offers the same utility. -- John Wiegley FP Complete Haskell tools, training and consulting http://fpcomplete.com johnw on #haskell/irc.freenode.net