| Copyright | (c) Andy Gill 2001 (c) Oregon Graduate Institute of Science and Technology 2001 |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | libraries@haskell.org |
| Stability | experimental |
| Portability | portable |
| Safe Haskell | Safe |
| Language | Haskell98 |
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.