Mats Rauhala
I'm trying to grok continuation passing style, but for now it just seems to complicate and/or slow down code (stack)
In general CPS will even improve efficiency, in some cases asymptotically [1,2,3], but that's not their main point. Delimited continuations are the mother of all control constructs, so you can implement many kinds of control flow like concurrency (coroutines), resumable exceptions (or basic exceptions for that matter), forks and reunions, etc. Many Haskell abstractions make use of them; iteratees to name one, on which I rely heavily. Also most of the libraries I upload to Hackage use continuations a lot. For a web application continuations help a lot with some of the difficulties of the stateless HTTP, for example form processing and session management. Along with every link goes a continuation, which is the logical future of the computation. This enables you to write your web application almost totally disregarding the statelessness, like your application would talk to a local user on a terminal. The user session becomes a coroutine of the web server. [1] http://www.iai.uni-bonn.de/~jv/mpc08.pdf [2] http://hackage.haskell.org/package/monad-ran [3] http://comonad.com/reader/2011/free-monads-for-less/ Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/