On Tue, Jan 10, 2006 at 05:28:03PM +0000, Chris Kuklewicz wrote:
I'll make a guess...
Ian Lynagh wrote:
Hi all,
foo :: String -> (String, String) foo = runState bar
bar :: SecondMonad String bar = do inp <- get case inp of [] -> return [] x:xs -> do put xs liftM (x:) bar The liftM should be equivalent to temp <- bar return ( (x:) temp )
It looks like the first call to foo will have bar consuming the entire input string.
I'm not entirely sure what you mean here. The result will be the entire input string, but State is a lazy monad, so it won't have to consume it all before it starts returning it. For example, if you replace the definition of foo with foo xs = (evalState bar xs, "") then the program runs in constant space (but this isn't a solution to the real problem, as bar will only consume a prefix of the string there). Thanks Ian