kowainik / unlift

🛗 Typeclass for monads that can be unlifted to arbitrary base monads

unlift

Typeclass for monads that can be unlifted to arbitrary base monads:

class (MonadBase b m) => MonadUnlift b m
  where
    withRunInBase :: ((forall a . m a -> b a) -> b x) -> m x

This typeclass is helpful when writing code that is polymorphic over the base monad, so later you can select a different base monad for each specific use-case.

Common usages include:

1. Concurrent testing with dejafu.
2. Working with code over polymorphic PrimMonad.

unlift's Issues

Implement MonadUnlift

How to use this library with co-log?

I noticed that co-log has no askLogAction that I can use to pull out the logger configuration before dropping to IO in functions like withCurrentDirectory and then re-invoking usingLoggerT logAction to get into the logger monad.

Is unlift the right approach to handle this problem? If so it would be good to have an example in the README.