| Portability | portable |
|---|---|
| Stability | experimental |
| Maintainer | ross@soi.city.ac.uk |
| Safe Haskell | Safe-Inferred |
Control.Monad.Trans
Description
Classes for monad transformers.
A monad transformer makes new monad out of an existing monad, such
that computations of the old monad may be embedded in the new one.
To construct a monad with a desired set of features, one typically
starts with a base monad, such as Identity, [] or IO, and
applies a sequence of monad transformers.
Most monad transformer modules include the special case of applying the
transformer to Identity. For example, State s is an abbreviation
for StateT s Identity.
Each monad transformer also comes with an operation runXXX to
unwrap the transformer, exposing a computation of the inner monad.