On 8/1/07, Andrew Wagner
you can imagine each of the calls to putStrLn gets implicitly passed a variable (here, the world ) and they happen in succession so it's "like a loop".
It breaks down further as soon as you add any amount of complexity to the code as well. E.g.: [....] Not loop-ish at all!
I totally agree I was just stating how I understood the original poster's statement :) Personally I showed haskell to a Friend last week end. To explain some monadic code I explained it somewhat this way ( please keep in mind that I'm a beginner so the explanation I gave him is probably not accurate ) I told him that in a lazy functional programming language you can't decide when a function gets evaluated or not. I then told him that it gets problematic if you want evaluate some functions in sequence. I also told him that haskell is a pure language, that is there is no side effects in the functions. I then told him that it's a problem if you want to interact with the outside world (IO) I explained that a monad is a way to get functions evaluated in a specific order, with a type such that you can't mix actions with pure functions. I told him that monads are just a special datatype and implementation of 2 functions : - a function that lets you evaluate a function before evaluating the next one, taking the output of the first function to feed the input of the second. - a function that takes a pure value and "promotes" to the monad's type. I told him that in the case of IO the datatype in question is IO and it contains data about the outside world, but there are many other monads, but I didn't go there too much because it's not totally clear for me. He seemed to be not too much confused by the concept, so I hope that I didn't told him too much inaccuracies...