Hi Radosław,
You should be able to write this with MaybeT as follows:
getStrip :: IO ( Maybe String )
getStrip = runMaybeT $ do
pageContent <- liftIO $ downloadFile mainPageAddress
let x = patternForStrip pageContent
print x
z <- x
liftIO $ downloadFile $ mainPageAddress ++ z
If you can do without the 'print', you should be able to write it as:
getStrip :: IO ( Maybe String )
getStrip = runMaybeT $ do
pageContent <- liftIO $ downloadFile mainPageAddress
z <- patternForStrip pageContent
liftIO $ downloadFile $ mainPageAddress ++ z
You can find MaybeT here:
http://www.haskell.org/haskellwiki/New_monads/MaybeT
Best,
- Benja
On 11/18/07, Radosław Grzanka
Hello, I am writing some toys programs to learn and try to apply Monads properties (without success, I must say). Although I spent half a day on this code:
I couldn't simplify (shorten) getStrip function. After reading "Doing it with class" ( http://www.haskell.org/all_about_monads/html/class.html ) I had an impression that I could "collapse" cases using some Monads properties. But maybe I misunderstood something.
Can anyone look at it and give me a pointers?? (I don't mind if the code becomes unreadable a bit.)
Thank you, Radek. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe