fclabels-0.4.2: First class accessor labels. Source code Contents Index

Data.Record.Label

Contents Getter, setter and modifier types. Label type. Bidirectional functor. State monadic label operations. Derive labels using Template Haskell.

Synopsis

type Getter f o = f -> o type Setter f i = i -> f -> f type Modifier f i o = (o -> i) -> f -> f data Point f i o newtype f :-> a = Label (Point f a a) label :: Getter f a -> Setter f a -> f :-> a get :: (f :-> a) -> f -> a set :: (f :-> a) -> a -> f -> f mod :: (f :-> a) -> (a -> a) -> f -> f fmapL :: Applicative f => (a :-> b) -> f a :-> f b data a :<->: b = Lens { fw :: a -> b bw :: b -> a } (<->) :: (a -> b) -> (b -> a) -> a :<->: b class Iso f where iso :: (a :<->: b) -> f a -> f b osi :: (a :<->: b) -> f b -> f a lmap :: Functor f => (a :<->: b) -> f a :<->: f b for :: (i -> o) -> (f :-> o) -> Point f i o getM :: MonadState s m => (s :-> b) -> m b setM :: MonadState s m => (s :-> b) -> b -> m () modM :: MonadState s m => (s :-> b) -> (b -> b) -> m () (=:) :: MonadState s m => (s :-> b) -> b -> m () mkLabels :: [Name] -> Q [Dec]

Getter, setter and modifier types.

type Getter f o = f -> o Source

type Setter f i = i -> f -> f Source

type Modifier f i o = (o -> i) -> f -> f Source

Label type.

data Point f i o Source

Instances Functor (Point f i) Applicative (Point f i)

newtype f :-> a Source

Constructors Label (Point f a a) Instances Category :-> Iso (:-> i)

label :: Getter f a -> Setter f a -> f :-> a Source

get :: (f :-> a) -> f -> a Source

Get the getter function from a label.

set :: (f :-> a) -> a -> f -> f Source

Get the setter function from a label.

mod :: (f :-> a) -> (a -> a) -> f -> f Source

Get the modifier function from a label.

fmapL :: Applicative f => (a :-> b) -> f a :-> f b Source

Bidirectional functor.

data a :<->: b Source

The lens datatype, a function that works in two directions. To bad there is no convenient way to do application for this. Constructors Lens fw :: a -> b bw :: b -> a Instances Category :<->: Iso (:<->: i)

(<->) :: (a -> b) -> (b -> a) -> a :<->: b Source

Constructor for lenses.

class Iso f where Source

This isomorphism type class is like a Functor but works in two directions. Methods iso :: (a :<->: b) -> f a -> f b Source osi :: (a :<->: b) -> f b -> f a Source Instances Iso (:<->: i) Iso (:-> i)

lmap :: Functor f => (a :<->: b) -> f a :<->: f b Source

for :: (i -> o) -> (f :-> o) -> Point f i o Source

Combine a partial destructor with a label into something easily used in the applicative instance for the hidden Point datatype. Internally uses the covariant in getter, contravariant in setter bi-functioral-map function. (Please refer to the example because this function is just not explainable on its own.)

State monadic label operations.

getM :: MonadState s m => (s :-> b) -> m b Source

Get a value out of state pointed to by the specified label.

setM :: MonadState s m => (s :-> b) -> b -> m () Source

Set a value somewhere in state pointed to by the specified label.

modM :: MonadState s m => (s :-> b) -> (b -> b) -> m () Source

Modify a value with a function somewhere in state pointed to by the specified label.

(=:) :: MonadState s m => (s :-> b) -> b -> m () Source

Alias for setM that reads like an assignment.

Derive labels using Template Haskell.

mkLabels :: [Name] -> Q [Dec] Source

Derive labels for all the record selector in a datatype.

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