Excerpts from jean-christophe mincke's message of Tue Nov 10 21:18:34 +0100 2009:
Hello, Hello,
I would like to get some advice about state monad (or any other monad I guess) and CPS.
Here is to remarks somewhat off topic: [...]
walk Empty acc k = k acc walk (Leaf _) acc k = k (acc+1) walk (Node (l, _, r)) acc k = let k1 acc = walk r acc k in walk l (acc+1) k1
Remember that by default laziness and accumulators does not fits well together. Here you are probably building a chain of thunks. Making acc a strict argument (using !acc) or using 'seq' (acc `seq` ...) will cure this. [...]
do acc <- get put (acc+1) ...
Since this pattern occurs often 'modify' is a combination of get and put: do modify (+1) ... About your CPS question, you should have a look at the 'transformers' package, in particular the Control.Monad.Trans.Cont [1] module. [1]: http://hackage.haskell.org/packages/archive/transformers/0.1.4.0/doc/html/Co... Best regards, -- Nicolas Pouillard http://nicolaspouillard.fr