Ether: Monad Transformers and Classes

In Short Ether is a Haskell library that extends mtl and transformers with tagged monad transformers and classes. Here are some resources to learn about the concept: Blog post Tagging Monad Transformer Layers by Dan Piponi Paper PDF Monad Factory: Type-Indexed Monads by Mark Snyder, Perry Alexander See also Roman Cheplyaka's blog post The problem with mtl to see what exactly is the problem we're s