Lazy -mtl +transformers

module Control.Monad.Trans.RWS.Lazy
transformers Control.Monad.Trans.RWS.Lazy
A monad transformer that combines ReaderT, WriterT and StateT. This version is lazy; for a strict version, see Control.Monad.Trans.RWS.Strict, which has the same interface.
module Control.Monad.Trans.State.Lazy
transformers Control.Monad.Trans.State.Lazy
Lazy state monads, passing an updatable state through a computation. See below for examples. In this version, sequencing of computations is lazy. For a strict version, see Control.Monad.Trans.State.Strict, which has the same interface. Some computations may not require the full power of state transformers: * For a read-only state, see Control.Monad.Trans.Reader. * To accumulate a value without using it on the way, see Control.Monad.Trans.Writer.
module Control.Monad.Trans.Writer.Lazy
transformers Control.Monad.Trans.Writer.Lazy
The lazy WriterT monad transformer, which adds collection of outputs (such as a count or string output) to a given monad. This version builds its output lazily; for a strict version, see Control.Monad.Trans.Writer.Strict, which has the same interface. This monad transformer provides only limited access to the output during the computation. For more general access, use Control.Monad.Trans.State instead.