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
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)
src/HAppS/Examples/HTTP1.hs. 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.
Attachment (https1-whatsnew): application/octet-stream, 1933 bytes Attachment (HTTP1.hs): application/octet-stream, 4794 bytes
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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.