In general, if you want to *dynamically generate* actions depending on the result of an earlier action you will always encounter join/(>>=). For example (with ReadPrec/Parser): I want to first parse a character, and then parse the same character two more times. numberAndThenThatManyAs = join (fmap (\c -> satisfy (==c) *> satisfy (==c)) char) Of note: * The example is contrived for simplicity's sake, but you do really need a Monad (and hence join) to perform stuff like this in general. A more practical example would be parsing command-line options that depend on previous options. * Obviously it's way more humane to write this with do-syntax. (or (>>=) or something) - do { c <- char; satisfy (==c); satisfy (==c) } * I'm not actually sure whether you need a Monad in this situation, maybe you could get away with just selectives http://hackage.haskell.org/package/selective-0.3 ======= Georgi