[Haskell-cafe] Re: Foralls in records

Chris Kuklewicz haskell at list.mightyreason.com
Wed Mar 14 10:58:30 EDT 2007

> I can't seem to find any examples of how to actually implement liftIO for a 
> monad. Any ideas/pointers?

Searching the haskell wiki for MonadIO gives several examples.


> instance MonadIO m => MonadIO (ExitT e m) where
>   liftIO = lift . liftIO

Where you can see you are just delegating the work of the transformer to the
underlying monad.  Eventually it hits the bottom of the stack and sees:

> instance MonadIO IO where
>   liftIO = id

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