[Haskell-beginners] confused by <-

Bryce Verdier bryceverdier at gmail.com
Thu Sep 27 02:31:46 CEST 2012

On 9/26/12 4:53 PM, Ertugrul Söylemez wrote:
> Bryce Verdier <bryceverdier at gmail.com> wrote:
>> This is the new code that is trying to use try (imported from
>> Control.Exception)
>> getGoogR = do
>>       body <- try {- [...] -}
>> [...]
>> 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.
> The fix is indeed simple.  In fact you're just using the wrong 'try',
> because Yesod handlers aren't IO actions, but actions in a monad that is
> specific to your application, called Handler.  The error message
> suggests that, although the type is spelled out completely there.
> What you want is the lifted version of 'try', which you find in the
> Control.Exception.Lifted module.
> Greets,
> Ertugrul

Thank you for the reply Ertugrul, sadly that didn't seem to help. :(

Here are my changes:
import qualified Control.Exception.Lifted as L

     body <- L.try (simpleHttp "http://www.google.com") :: IO (Either 
L.SomeException Data.ByteString.Lazy.Internal.ByteString)

I did the full qualified because the first time I tried your suggestion 
I just "Control.Exception.Lifted" and I got the same error as I'm 
sharing below.

     Couldn't match expected type `IO b0'
                 with actual type `GHandler sub0 master0 RepJson'
     In the expression:

Thanks for being willing to help me with this.

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