Re: performance of monads

I see a lot of literature that says that monads "simulate" the effects of imperative programming concepts.

I think that's just bad wording. To take a rather trite point of view, in a language such as C /everything/ is done within a monad, and all types, even int, are really IO something (IO Int). In Haskell you may see costs associated with using Monads, but they are mainly to do with dealing with the difficulties that arise from having laziness everywhere. Jón -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk 31 Chalmers Road jf@cl.cam.ac.uk Cambridge CB1 3SZ +44 1223 570179 (after 14:00 only, please!)