[Haskell-beginners] confused by <-

26 Sep 2012

      I'm trying to play with a Yesod application. I had working code before, 
but tried stretching myself a bit and adding in some error checking.

This code worked:

getGoogR = do
     body <- simpleHttp "http://www.google.com"
     jsonToRepJson $ object ["response" .= (showDigest $ sha1 body)]

This is the new code that is trying to use try (imported from 
Control.Exception)
getGoogR = do
     body <- try (simpleHttp "http://www.google.com") :: IO (Either 
SomeException Data.ByteString.Lazy.Internal.ByteString)
     case body of
         Left _ -> jsonToRepJson $ object ["response" .= ( show "ERROR: 
NO DATA FOR ONE REASON OR ANOTHER")]
         Right val -> jsonToRepJson $ object ["response" .= (showDigest 
$ sha1 val)]

and I get this error:
     Couldn't match expected type `IO b0'
                 with actual type `GHandler sub0 master0 RepJson'
     In the expression:
       jsonToRepJson
       $ object
           ["response" .= (show "ERROR: NO DATA FOR ONE REASON OR ANOTHER")]
     In a case alternative:
         Left _
           -> jsonToRepJson
              $ object
                  ["response" .= (show "ERROR: NO DATA FOR ONE REASON OR 
ANOTHER")]
     In a stmt of a 'do' block:
       case body of {
         Left _
           -> jsonToRepJson
              $ object
                  ["response" .= (show "ERROR: NO DATA FOR ONE REASON OR 
ANOTHER")]
         Right val
           -> jsonToRepJson $ object ["response" .= (showDigest $ sha1 
val)]

I'm sure that my problem has a simple fix, but I just don't know what it 
is. I will be happy to share any other code if people ask, I'm just 
giving the short version for brevities sake.

Thanks in advance,
Bryce

[Haskell-beginners] confused by <-

Bryce Verdier