On 12/20/07, Joost Behrends
makes a DESTRUCTIVE UPDATE of the DivIters (by put) and this kind of recursion seems not to "remember" itself (as i have understood, that is achieved by "tail recursion"). I just didn't like making DivIters to States. It's kind of lying code.
I just want to point out that this isn't true; "put" in the State monad doesn't do any destructive update at all (unlike, for example, IORef). You can tell this for yourself by looking at the type of "State s a" in Control.Monad.State: http://haskell.org/ghc/docs/latest/html/libraries/mtl/src/Control-Monad-Stat... newtype State s a = State { runState :: s -> (a,s) } That is, your "divisions" function of type divisions :: State DivIter DivIter is equivalent to the type runState divisions :: DivIter -> (DivIter, DivIter) and the code is the same as if you'd just passed the DivIter directly along. -- ryan