Regardless of what monad is transformed by StateT, I think the OP's issue remains.
modify below is straight from Gill's source at http://darcs.haskell.org/packages/ modify :: (MonadState s m) => (s -> s) -> m () modify f = do s <- get put (f s) we could add modifyM :: (MonadState s m) => (s -> m s) -> m () modifyM f = do s <- get s' <- f s put s' which I think you could use... modifyM is just a bit more flexible than Cale's liftModify, I think. On 11/8/06, Max Vasin <[EMAIL PROTECTED]> wrote:
>>>>> "Peter" == Peter Steiner <[EMAIL PROTECTED]> writes: Peter> On 11/8/06, Bulat Ziganshin <[EMAIL PROTECTED]> wrote: >> Hello Peter, >> >> Wednesday, November 8, 2006, 1:48:24 PM, you wrote: >> >> > i would like to be able to debug what's happening inside the >> modifier > function. that's why i want to be able to use a >> modifier that's in the > IO monad >> >> for debugging there is 'trace' function which don't needs IO >> monad Peter> thanks. i am aware of trace, but the potentially messed up Peter> execution order makes it very hard for me to get useful Peter> information out of the resulting trace. besides, IO will Peter> scale to more elaborate logging mechanisms later on... If all you want from IO is logging why not just use MonadWriter? -- WBR, Max Vasin. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
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