Haskell HTTP client using ByteString

I am making HTTP requests and I want to get the corresponding responses as ByteString instead of String. I am using HTTP-4000.2.18 .

As far as I can tell, this is exactly what BufferType is for:

to give the user freedom to present the content of the request and response

However, I don't understand how to do this. Here's what I have so far: I am building queries with a function called getLazyRequest

like this:

getLazyRequest
    :: String                   -- ^URL to fetch
    -> Request Lazy.ByteString  -- ^The constructed request

      

        
        
        
      

    

and then I should be able to pass requests directly to simpleHTTP . GetLazyRequest is identical to getRequest , except that it returns a ByteString request instead of a String. But it doesn't work.

Full source:

import Network.HTTP
import Network.URI ( parseURI )
import qualified Data.ByteString.Lazy as Lazy
import Network.BufferType ( BufferOp(..), BufferType(..) )


main = do
    let req = getLazyRequest "http://hackage.haskell.org/"
    rsp <- simpleHTTP req
    line <- fmap (take 100) (getResponseBody rsp)
    putStrLn ""


getLazyRequest
    :: String                   -- ^URL to fetch
    -> Request Lazy.ByteString  -- ^The constructed request
getLazyRequest urlString =
  case parseURI urlString of
    Nothing -> error ("getLazyRequest: Not a valid URL - " ++ urlString)
    Just u  -> mkRequest GET u

      

        
        
        
      

    

Errors:

No instance for (HStream Lazy.ByteString)
  arising from a use of `simpleHTTP'
Possible fix:
  add an instance declaration for (HStream Lazy.ByteString)
In a stmt of a 'do' block: rsp <- simpleHTTP req

No instance for (BufferType Lazy.ByteString)
  arising from a use of `mkRequest'
Possible fix:
  add an instance declaration for (BufferType Lazy.ByteString)
In the expression: mkRequest GET u
In a case alternative: Just u -> mkRequest GET u

      

        
        
        
      

    

I don't understand why these errors are, since Lazy.ByteString is an instance of HStream and BufferType .

EDIT

Indeed, I have to install bytestring versions. Is it possible that I installed one with sudo and the other with my user?

$ ghc-pkg list bytestring
/var/lib/ghc/package.conf.d
   bytestring-0.9.2.1
/home/adizere/.ghc/x86_64-linux-7.4.1/package.conf.d
   bytestring-0.10.4.1

      

        
        
        
      

    

I couldn't unregister either of these two versions, so I cabled the code instead and it seems to work now.