martin wrote:
I am trying to understand the ideas of Koen Klaessen, published in Functional Pearls: "A poor man's concurrency" (1993).
The code in the paper doesn't compile. E.g. uses "lambda dot" instead of "labmda arrow", i.e. the way the labmda calculus guys write things. Was that ever legal haskell or is this the result of some lhs2lex pretty printer?
Anyways, I believe I was able to convert that into modern haskell syntax - at least it compiles. But I have trouble to understand the Monad instance presented there. Could anyobody walk me through the bind function?
But even more important: how do you guys develop an intuition about what the bind operator does in a specific monad.
I find it very helpful to think of monads as "lists of instructions". I have written a thorough and hopefully accessible explanation here http://apfelmus.nfshost.com/articles/operational-monad.html which also discusses a transparent implementation Koen Classen's parser combinators. From this point of view, the continuation monad corresponds to a particular list implementation, namely "difference lists". If you have trouble understanding the continuation monad, I would recommend to go via the "list of instructions" route, as it involves only functions of a less higher order. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com