[Haskell-cafe] How does one read complicated type signatures?

Jakub Arnold darthdeus at gmail.com
Fri Jan 24 03:54:35 UTC 2014

Hello world,  

I’ve just started playing with the http-conduit package and started inspecting type signatures of some of the functions, and I stumbled upon many things that look like this

*Main Network.HTTP.Conduit> :t withManager
  :: (monad-control-
        IO m,
      transformers- m) =>
      -> resourcet-0.4.10:Control.Monad.Trans.Resource.Internal.ResourceT
           m a)
     -> m a

The question is … how am I supposed to read these? It seems that they wrap around (maybe) 80 characters, which makes them unreadable … and the package prefixes also don’t really help.

I’d like to point out here that I’m really a noob without any practical experience in Haskell, I’ve just read a few books. So I don’t have a problem understanding the concepts, but more and more often I find myself struggling just to read the type signature correctly

Thanks for any tips, Jakub
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