Control.Applicative.Lift

transformers-0.6.1.2: Concrete functor and monad transformers

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 | Haskell2010

Control.Applicative.Lift

Contents

- Lifting an applicative
- Collecting errors

Description

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

Synopsis

- data Lift (f :: Type -> Type) a
  - = Pure a
  - | Other (f a)
- unLift :: Applicative f => Lift f a -> f a
- mapLift :: (f a -> g a) -> Lift f a -> Lift g a
- elimLift :: (a -> r) -> (f a -> r) -> Lift f a -> r
- type Errors e = Lift (Constant e :: Type -> Type)
- runErrors :: Errors e a -> Either e a
- failure :: e -> Errors e a
- eitherToErrors :: Either e a -> Errors e a

# Lifting an applicative

data Lift (f :: Type -> Type) a Source #

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

Constructors

Pure a |
Other (f a) |

#### Instances

Instances details

Generic1 (Lift f :: Type -> Type) Source # |
Instance details Defined in Control.Applicative.Lift Associated Types
type Rep1 (Lift f :: Type -> Type) |
Instance details Defined in Control.Applicative.Lift type Rep1 (Lift f :: Type -> Type) = D1 ('MetaData "Lift" "Control.Applicative.Lift" "transformers-0.6.1.2-3e4b" 'False) (C1 ('MetaCons "Pure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1) :+: C1 ('MetaCons "Other" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 f)))
Methods from1 :: Lift f a -> Rep1 (Lift f) a # to1 :: Rep1 (Lift f) a -> Lift f a #
Foldable1 f => Foldable1 (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods fold1 :: Semigroup m => Lift f m -> m Source # foldMap1 :: Semigroup m => (a -> m) -> Lift f a -> m Source # foldMap1' :: Semigroup m => (a -> m) -> Lift f a -> m Source # toNonEmpty :: Lift f a -> NonEmpty a Source # maximum :: Ord a => Lift f a -> a Source # minimum :: Ord a => Lift f a -> a Source # head :: Lift f a -> a Source # last :: Lift f a -> a Source # foldrMap1 :: (a -> b) -> (a -> b -> b) -> Lift f a -> b Source # foldlMap1' :: (a -> b) -> (b -> a -> b) -> Lift f a -> b Source # foldlMap1 :: (a -> b) -> (b -> a -> b) -> Lift f a -> b Source # foldrMap1' :: (a -> b) -> (a -> b -> b) -> Lift f a -> b Source #
Eq1 f => Eq1 (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods liftEq :: (a -> b -> Bool) -> Lift f a -> Lift f b -> Bool Source #
Ord1 f => Ord1 (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods liftCompare :: (a -> b -> Ordering) -> Lift f a -> Lift f b -> Ordering Source #
Read1 f => Read1 (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods 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 # |
Instance details Defined in Control.Applicative.Lift Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Lift f a -> ShowS Source # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Lift f a] -> ShowS Source #
Alternative f => Alternative (Lift f) Source # | A combination is `Pure` only either part is.
Instance details Defined in Control.Applicative.Lift Methods empty :: Lift f a # (<|>) :: Lift f a -> Lift f a -> Lift f a # some :: Lift f a -> Lift f [a] # many :: Lift f a -> Lift f [a] #
Applicative f => Applicative (Lift f) Source # | A combination is `Pure` only if both parts are.
Instance details Defined in Control.Applicative.Lift Methods pure :: a -> Lift f a # (<*>) :: Lift f (a -> b) -> Lift f a -> Lift f b # liftA2 :: (a -> b -> c) -> Lift f a -> Lift f b -> Lift f c # (*>) :: Lift f a -> Lift f b -> Lift f b # (<*) :: Lift f a -> Lift f b -> Lift f a #
Functor f => Functor (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods fmap :: (a -> b) -> Lift f a -> Lift f b # (<$) :: a -> Lift f b -> Lift f a #
Foldable f => Foldable (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods fold :: Monoid m => Lift f m -> m # foldMap :: Monoid m => (a -> m) -> Lift f a -> m # foldMap' :: Monoid m => (a -> m) -> Lift f a -> m # foldr :: (a -> b -> b) -> b -> Lift f a -> b # foldr' :: (a -> b -> b) -> b -> Lift f a -> b # foldl :: (b -> a -> b) -> b -> Lift f a -> b # foldl' :: (b -> a -> b) -> b -> Lift f a -> b # foldr1 :: (a -> a -> a) -> Lift f a -> a # foldl1 :: (a -> a -> a) -> Lift f a -> a # toList :: Lift f a -> [a] # null :: Lift f a -> Bool # length :: Lift f a -> Int # elem :: Eq a => a -> Lift f a -> Bool # maximum :: Ord a => Lift f a -> a # minimum :: Ord a => Lift f a -> a # sum :: Num a => Lift f a -> a # product :: Num a => Lift f a -> a #
Traversable f => Traversable (Lift f) Source # |
Instance details Defined in Control.Applicative.Lift Methods traverse :: Applicative f0 => (a -> f0 b) -> Lift f a -> f0 (Lift f b) # sequenceA :: Applicative f0 => Lift f (f0 a) -> f0 (Lift f a) # mapM :: Monad m => (a -> m b) -> Lift f a -> m (Lift f b) # sequence :: Monad m => Lift f (m a) -> m (Lift f a) #
(Eq1 f, Eq a) => Eq (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift Methods (==) :: Lift f a -> Lift f a -> Bool # (/=) :: Lift f a -> Lift f a -> Bool #
(Ord1 f, Ord a) => Ord (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift Methods compare :: Lift f a -> Lift f a -> Ordering # (<) :: Lift f a -> Lift f a -> Bool # (<=) :: Lift f a -> Lift f a -> Bool # (>) :: Lift f a -> Lift f a -> Bool # (>=) :: Lift f a -> Lift f a -> Bool # max :: Lift f a -> Lift f a -> Lift f a # min :: Lift f a -> Lift f a -> Lift f a #
Generic (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift Associated Types
type Rep (Lift f a) |
Instance details Defined in Control.Applicative.Lift type Rep (Lift f a) = D1 ('MetaData "Lift" "Control.Applicative.Lift" "transformers-0.6.1.2-3e4b" 'False) (C1 ('MetaCons "Pure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Other" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (f a))))
Methods from :: Lift f a -> Rep (Lift f a) x # to :: Rep (Lift f a) x -> Lift f a #
(Read1 f, Read a) => Read (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift Methods readsPrec :: Int -> ReadS (Lift f a) # readList :: ReadS [Lift f a] # readPrec :: ReadPrec (Lift f a) # readListPrec :: ReadPrec [Lift f a] #
(Show1 f, Show a) => Show (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift Methods showsPrec :: Int -> Lift f a -> ShowS # show :: Lift f a -> String # showList :: [Lift f a] -> ShowS #
type Rep1 (Lift f :: Type -> Type) Source # |
Instance details Defined in Control.Applicative.Lift type Rep1 (Lift f :: Type -> Type) = D1 ('MetaData "Lift" "Control.Applicative.Lift" "transformers-0.6.1.2-3e4b" 'False) (C1 ('MetaCons "Pure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1) :+: C1 ('MetaCons "Other" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 f)))
type Rep (Lift f a) Source # |
Instance details Defined in Control.Applicative.Lift type Rep (Lift f a) = D1 ('MetaData "Lift" "Control.Applicative.Lift" "transformers-0.6.1.2-3e4b" 'False) (C1 ('MetaCons "Pure" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: C1 ('MetaCons "Other" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (f a))))

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.

elimLift :: (a -> r) -> (f a -> r) -> Lift f a -> r Source #

Eliminator for `Lift`.

-     elimLift f g . pure = f

-     elimLift f g . Other = g

# Collecting errors

type Errors e = Lift (Constant e :: Type -> Type) 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.

-     pure f <*> pure x = pure (f x)

-     pure f <*> failure e = failure e

-     failure e <*> pure x = failure e

-     failure e1 <*> failure e2 = failure (e1 <> e2)

runErrors :: Errors e a -> Either e a Source #

Extractor for computations with accumulating errors.

-     runErrors (pure x) = Right x

-     runErrors (failure e) = Left e

failure :: e -> Errors e a Source #

Report an error.

eitherToErrors :: Either e a -> Errors e a Source #

Convert from `Either` to `Errors` (inverse of `runErrors`).