Copyright | (c) Ross Paterson 2010 |
---|---|

License | BSD-style (see the file LICENSE) |

Maintainer | R.Paterson@city.ac.uk |

Stability | experimental |

Portability | portable |

Safe Haskell | Safe |

Language | Haskell98 |

Adding a new kind of pure computation to an applicative functor.

# Lifting an applicative

Applicative functor formed by adding pure computations to a given applicative functor.

## Instances

unLift :: Applicative f => Lift f a -> f a Source #

Projection to the other functor.

mapLift :: (f a -> g a) -> Lift f a -> Lift g a Source #

Apply a transformation to the other computation.

# Collecting errors

type Errors e = Lift (Constant e) Source #

An applicative functor that collects a monoid (e.g. lists) of errors.
A sequence of computations fails if any of its components do, but
unlike monads made with `ExceptT`

from Control.Monad.Trans.Except,
these computations continue after an error, collecting all the errors.