Brandon,
Thanks you for your advice.
I want to add CGI support to a program that writes to a file, but has no network access. The old code uses a WriterT with IO in it. Adding another monad to the stack with IO to the network, is a bit too difficult for a beginner like me.
The old code returns IO [String] ([String] = list of status messages). It is a bit annoying that I have to adapt the old code. I just want to grab the status messages and convert them to html and write them to the network.
I wonder, do you always have to create a monadtransformer if your program uses 2 kinds of IO?
Kees
Van: Beginners [mailto:beginners-bounces@haskell.org] Namens Brandon Allbery
Verzonden: maandag 14 oktober 2013 17:03
Aan: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell
Onderwerp: Re: [Haskell-beginners] monads do not fit together?
On Mon, Oct 14, 2013 at 10:58 AM, Kees Bleijenberg <k.bleijenberg@lijbrandt.nl> wrote:
I get the same message (Couldn't match expected type `CGIT IO a0' with actual type `IO [String]'). I think I do understand where this message is coming from. But what can I do to fix it?
For now, you just correct the type of runRefreshFirewall; it should be
runRefreshFirewall :: String -> CGIT IO [String]
If you are intending to run actual IO actions in the real thing, you'll need to use liftIO to "reach" the IO embedded in the CGIT IO a.
--
brandon s allbery kf8nh sine nomine associates
unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net