fclabels-0.3.0: First class accessor labels. Source code Contents Index

Data.Record.Label

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

Synopsis

type Getter a b = a -> b type Setter a b = b -> a -> a type Modifier a b = (b -> b) -> a -> a data a :-> b = Label { lget :: Getter a b lset :: Setter a b lmod :: Modifier a b } mkModifier :: Getter a b -> Setter a b -> Modifier a b mkLabel :: Getter a b -> Setter a b -> a :-> b idL :: a :-> a (%) :: (g :-> a) -> (f :-> g) -> f :-> a class Lens f where lmap :: (a -> b, b -> a) -> f a -> f b (%%) :: Functor f => (a :-> b) -> (g :-> f a) -> g :-> f b 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 () list :: Int -> [a] :-> a maybeNull :: [a] :-> Maybe [a] mkLabels :: [Name] -> Q [Dec]

Getter, setter and modifier types.

type Getter a b = a -> b Source

type Setter a b = b -> a -> a Source

type Modifier a b = (b -> b) -> a -> a Source

Label type.

data a :-> b Source

Constructors Label lget :: Getter a b lset :: Setter a b lmod :: Modifier a b Instances Category :-> Lens (:-> f)

mkModifier :: Getter a b -> Setter a b -> Modifier a b Source

Create a modifier function out of a getter and a setter.

mkLabel :: Getter a b -> Setter a b -> a :-> b Source

Smart constructor for Labels, the modifier will be computed based on getter and setter.

Identity and composition.

idL :: a :-> a Source

(%) :: (g :-> a) -> (f :-> g) -> f :-> a Source

Bidirectional functor.

class Lens f where Source

Methods lmap :: (a -> b, b -> a) -> f a -> f b Source Instances Lens (:-> f)

(%%) :: Functor f => (a :-> b) -> (g :-> f a) -> g :-> f b Source

Apply label to lifted value and join afterwards.

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.

Useful example labels.

list :: Int -> [a] :-> a Source

maybeNull :: [a] :-> Maybe [a] Source

Derive labels using Template Haskell.

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

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