monadbi

This module provides a Class called MonadBi which acts as a superset of MonadTrans, and provides raise analogous to lift, i.e. lifts underlying monads into the transformer. It also provides lower which is the opposite of lift, and extracts underlying monads from monad transformers. Generally speaking, MonadBi represents the relationship between monads that can be transformed into each other (atleast partially). Natural instances are provided for many Monad Transformers.