Control.Lens.Action.Type

Getters and Folds

type Action m s a = forall f r. Effective m r f => (a -> f a) -> s -> f s

An Action is a Getter enriched with access to a Monad for side-effects.

Every Getter can be used as an Action.

You can compose an Action with another Action using (.) from the Prelude.

type MonadicFold m s a = forall f r. (Effective m r f, Applicative f) => (a -> f a) -> s -> f s

A MonadicFold is a Fold enriched with access to a Monad for side-effects.

A MonadicFold can use side-effects to produce parts of the structure being folded (e.g. reading them from file).

Every Fold can be used as a MonadicFold, that simply ignores the access to the Monad.

You can compose a MonadicFold with another MonadicFold using (.) from the Prelude.

type RelevantMonadicFold m s a = forall f r. (Effective m r f, Apply f) => (a -> f a) -> s -> f s

Indexed

type IndexedAction i m s a = forall p f r. (Indexable i p, Effective m r f) => p a (f a) -> s -> f s

An IndexedAction is an IndexedGetter enriched with access to a Monad for side-effects.

Every Getter can be used as an Action.

You can compose an Action with another Action using (.) from the Prelude.

type IndexedMonadicFold i m s a = forall p f r. (Indexable i p, Effective m r f, Applicative f) => p a (f a) -> s -> f s

An IndexedMonadicFold is an IndexedFold enriched with access to a Monad for side-effects.

Every IndexedFold can be used as an IndexedMonadicFold, that simply ignores the access to the Monad.

You can compose an IndexedMonadicFold with another IndexedMonadicFold using (.) from the Prelude.

type IndexedRelevantMonadicFold i m s a = forall p f r. (Indexable i p, Effective m r f, Apply f) => p a (f a) -> s -> f s

Index-Preserving

type IndexPreservingAction m s a = forall p f r. (Conjoined p, Effective m r f) => p a (f a) -> p s (f s)

An IndexPreservingAction can be used as a Action, but when composed with an IndexedTraversal, IndexedFold, or IndexedLens yields an IndexedMonadicFold, IndexedMonadicFold or IndexedAction respectively.

type IndexPreservingMonadicFold m s a = forall p f r. (Conjoined p, Effective m r f, Applicative f) => p a (f a) -> p s (f s)

An IndexPreservingFold can be used as a Fold, but when composed with an IndexedTraversal, IndexedFold, or IndexedLens yields an IndexedFold respectively.

type IndexPreservingRelevantMonadicFold m s a = forall p f r. (Conjoined p, Effective m r f, Apply f) => p a (f a) -> p s (f s)