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

Functor f => Functor (Lift f) Source # | |

Applicative f => Applicative (Lift f) Source # | A combination is |

Foldable f => Foldable (Lift f) Source # | |

fold :: Monoid m => Lift f m -> m Source # foldMap :: Monoid m => (a -> m) -> Lift f a -> m Source # foldr :: (a -> b -> b) -> b -> Lift f a -> b Source # foldr' :: (a -> b -> b) -> b -> Lift f a -> b Source # foldl :: (b -> a -> b) -> b -> Lift f a -> b Source # foldl' :: (b -> a -> b) -> b -> Lift f a -> b Source # foldr1 :: (a -> a -> a) -> Lift f a -> a Source # foldl1 :: (a -> a -> a) -> Lift f a -> a Source # toList :: Lift f a -> [a] Source # null :: Lift f a -> Bool Source # length :: Lift f a -> Int Source # elem :: Eq a => a -> Lift f a -> Bool Source # maximum :: Ord a => Lift f a -> a Source # minimum :: Ord a => Lift f a -> a Source # | |

Traversable f => Traversable (Lift f) Source # | |

Eq1 f => Eq1 (Lift f) Source # | |

Ord1 f => Ord1 (Lift f) Source # | |

Read1 f => Read1 (Lift f) Source # | |

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Lift f a) Source # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Lift f a] Source # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Lift f a) Source # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Lift f a] Source # | |

Show1 f => Show1 (Lift f) Source # | |

Alternative f => Alternative (Lift f) Source # | A combination is |

(Eq1 f, Eq a) => Eq (Lift f a) Source # | |

(Ord1 f, Ord a) => Ord (Lift f a) Source # | |

(Read1 f, Read a) => Read (Lift f a) Source # | |

(Show1 f, Show a) => Show (Lift f a) Source # | |

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.