Thanks Martin, that really helped. After many days reading the source, I'm still trying to grok HAppS. Meanwhile, here is a patch that adds examples to HAppS/Examples/HTTP1.hs for combining state and io, based on your advice. see especiallly the handler stateioH accepts an arbitrary state action, arbitrary io action, and a function for combining the two. Thomas. New patches: [add examples showing state and io thomas.hartman@db.com**20070906215844] { hunk ./src/HAppS/Examples/HTTP1.hs 7 +import System.Directory hunk ./src/HAppS/Examples/HTTP1.hs 68 + + ,h ["showbashrc"] GET $ ioshowH readbashrc + ,h ["showhttp1"] GET $ ioshowH readhttp1 + + ,h ["incrementstate"] GET $ stateH $ incnshow + ,h ["decrementstate"] GET $ stateH $ decnshow + ,h ["viewstate"] GET $ stateH view + + ,h ["showbashrc_and_inc"] GET $ stateioH incnshow readbashrc append_state + ,h ["showbashrc_and_dec"] GET $ stateioH decnshow readbashrc append_state + ,h ["showbashrc_and_view"] GET $ stateioH decnshow readbashrc append_state + hunk ./src/HAppS/Examples/HTTP1.hs 82 +append_state s io = io ++ "<BR>State: " ++ s + +incnshow = modify (+1) >> get >>=^ show +decnshow = modify (\x -> x-1) >> get >>=^ show +view = get >>=^ show + + +readbashrc = do + home <- getHomeDirectory + readfileSafe $ home ++ "/.bashrc" + +readhttp1 = readfileSafe "./HTTP1.hs" + +readfileSafe file = catch + ( readFile file >>=^ format_html ) + ( \e -> return ( show e ) ) + +stateioH stateaction ioaction combinestio = \() () -> do + stateresult <- stateaction + respond $ do + ioresult <- ioaction + showresult (combinestio stateresult ioresult) + + +stateH stateaction = ok $ \() () -> stateaction >>= respond + +ioshowH :: (Monad m, Show a) => IO a -> () -> () -> m (Either Request (IO Result)) +ioshowH ioaction = \() () -> respond $ do + ioresult <- ioaction + showresult ioresult + +showresult showable = sresult 200 (show showable) + + hunk ./src/HAppS/Examples/HTTP1.hs 151 + +format_html xs = concat $ map newlinetobr xs + where newlinetobr '\n' = "<br>" + newlinetobr x = [x] + +f >>=^ g = f >>= return . g } Martin Lütke Sent by: haskell-cafe-bounces@haskell.org 09/01/2007 07:04 PM To haskell-cafe@haskell.org cc Subject [Haskell-cafe] Re: wanted: HAppS example combining state and io Thomas Hartman writes:

In the latest happs (darcs pulled, updated head is 0.9.1 iirc), I am experimenting with the example file in

I would like to combine state with io. Eventually io will mean stuff like reading from a database, but for now I'm just reading a file. The example file HTTP1.hs has an example that demonstrates state with macid. I added an example that allows you to execute arbitrary io. I tried, but was unable to, add a handler that combines state and io.

, h ["iohandler"] GET $ ioReadFileHandler

, h ["statehandler"] GET $ stateHandler

--, h ["ioandstatehandler"] GET $ ioAndStateHandler ..... -- displays contents of HAPPS.hs in current directory ioReadFileHandler = iohandler $ readFile "./HAppS.hs" -- displays incremented state counter stateHandler = ok $ \() () ->

modify (+(1::Int)) >> get >>= respond . show -- should combine effect of iohandler with statehandler -- specifically, should display contents of HAppS.hs, and under that an incremented state handler -- is this possible ioAndStateHandler = undefined undefined Is mixing state and io possible with HAppS? If so, an example showing how to do it would be extremely helpful. best, thomas. ---This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error)

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I had no trouble getting this handler to work: h ["iohandler"] GET $ \() () -> do modify (+1) x <- get respond $ do cnts <- readFile "./sometext.txt" sresult 200 (cnts ++ show x) I believe the trick is that you cant mix io INTO the HAppS ServerPart monad. But from the ServerPart monad you can RETURN an io action. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.