2.2.2

• Control.Monad.Identity now re-exports Control.Monad.Trans.Identity
• Fix a bug in which Control.Monad.State.Class.modify' was not as strict in the new state as its counterparts in transformers
• Add a MonadError () Maybe instance
• Add liftEither :: MonadError e m => Either e a -> m a to Control.Monad.Except{.Class}
• Add a MonadWriter w ((,) w) instance (when built against base-4.9 or later)

2.2.1

• Provide MINIMAL pragmas for MonadState, MonadWriter, MonadReader
• Added a cyclic definition of ask in terms of reader for consistency with get/put vs. state and tell vs. writer
• Fix deprecation warnings caused by transformers 0.4 deprecating ErrorT.
• Added Control.Monad.Except in the style of the other mtl re-export modules

2.2.0.1

• Fixed a bug caused by the change in how transformers 0.4 exports its data types. We will now export runFooT for each transformer again!

2.2

• transformers 0.4 support
• Added instances for ExceptT
• Added modify' to Control.Monad.State.*

2.1.3.1

• Avoid importing Control.Monad.Instances on GHC 7.8 to build without deprecation warnings.

2.1.3

• Removed the now-irrelevant Error constraint from the MonadError instance for Either e.