Data.Label.Total

Default lenses for simple total getters and total possibly polymorphic, updates. Useful for creating accessor labels for single constructor datatypes. Also useful field labels that are shared between all the constructors of a multi constructor datatypes.

Documentation

type (:->) f o = Lens Total f o

Total lens type specialized for total accessor functions.

type Total = (->)

Context that represents computations that always produce an output.

lens

Arguments

:: (f -> o)

Getter.

-> ((o -> i) -> f -> g)

Modifier.

-> (f -> g) :-> (o -> i)

Create a total lens from a getter and a modifier.

We expect the following law to hold:

get l (set l a f) == a

set l (get l f) f == f

get :: ((f -> g) :-> (o -> i)) -> f -> o

Get the getter function from a lens.

modify :: ((f -> g) :-> (o -> i)) -> (o -> i) -> f -> g

Get the modifier function from a lens.

set :: ((f -> g) :-> (o -> i)) -> i -> f -> g

Get the setter function from a lens.

Working in contexts.

traverse :: Functor m => ((f -> g) :-> (o -> i)) -> (o -> m i) -> f -> m g

Modify in some context.

lifted :: Monad m => ((f -> g) :-> (m o -> m i)) -> ((o -> i) :-> (m a -> m b)) -> (f -> g) :-> (m a -> m b)

Lifted lens composition.

For example, useful when specialized to lists:

:: (f :-> [o])
-> (o :-> [a])
-> (f :-> [a])