Re: [Haskell-cafe] Explaining monads

Having just gone through all the tutorials and things (again but this time I think it stuck) the Haskell community is on the wrong track as far as teaching Monads to new programmers. If I were teaching addition and multiplication to children I wouldn't start with, "We'll begin by defining an algebraic structure named a "Group". From there we'll expand our concept to a "Ring" and "Field". A group is a set and a binary operator usually named "+" (or sometimes "*") such that...". No no no. You start with, "You all know how to count from one to 10. If we have 1 item and we 'add' another 1 item we have 2 items. We write this 1+1=2." The tutorials seriously need to step back and start with something like, "To enforce order of evaluation we evaluate closures* returning a defined type. The first closure will feed its result to the second which will in turn feed it's result to the third. Since the third closure can't be evaluated without having the results from the second and first (and thus they had to be evaluated earlier in time) we get a defined evaluation sequence. Here are some examples..." (* Even using the word 'closure' is scary for those not familiar with them.) Then, like "Monads For Functional Programming" (the paper that finally clicked Monads for me) you point out that evaluating all these closures returning a defined type in various ways form a structure (which you can then explain) and we can use that structure and change out the underlying effect(s) as needed. Now of course if your new programmer has the the necessary background you can throw them in the deep end. But don't do that to someone coming at the language from something like Java learned out of a business degree course. (My background is a CS degree with math minor and it still took two go-s at Haskell before I got as far as understanding what folks were talking about with Monads. Wish I had found Wadler's MFFP the first time around.) Where are the shallow end tutorials? (Don't get me wrong. The tutorials are good but there is also a place for the "learn-by-rote with lots of examples" ones too.) $0.02, -ljr PS - Not so much directed at Ronald's post but his was convenient to get me on my soapbox. Ronald Guida wrote:

My present goal is to understand monads well enough to be able to explain them to others. I wonder if it's possible to create a tutorial that explains monads well enough so that they just "make sense" or "click" for people. -- Lanny Ripple ScmDB / Cisco Systems, Inc.