The monad-wrap package
This package allows you to invoke a function on one monadic type passing it an argument of a different monadic type. The canonical example of this is wanting to use a function such as finally :: IO a -> IO a to catch exceptions thrown by a computation x :: ReaderT MyConfig IO b. If x uses the ReaderT function ask, it cannot be re-written to run in the IO monad, and hence cannot be executed with a construction like lift (x `finally` cleanup). Instead, you must use the wrap method, provide by module Control.Monad.Wrap. This package contains two further modules: Control.Monad.MultiWrap implements mwrap, a method that behaves like wrap but allows wrapping through multiple nested layers of monad transformer. The module Control.Monad.MultiLift provides mlift, a version of lift that similarly lifts through multiple nested monad transformers.
|Dependencies||base (==4.*), mtl (>=220.127.116.11 && <2) [details]|
|Uploaded||Sat Oct 17 22:11:52 UTC 2009 by DavidMazieres|
|Downloads||458 total (10 in the last 30 days)|
|Status||Docs uploaded by user
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