view package:lens-family

view :: Getter s t a b -> s -> a

Demote a lens or getter to a projection function.

view :: Monoid a => Fold s t a b -> s -> a

Returns the monoidal summary of a traversal or a fold.

views :: Monoid r => Fold s t a b -> (a -> r) -> s -> r

Given a fold or traversal, return the foldMap of all the values using the given function.

views :: Getter s t a b -> (a -> r) -> s -> r

views is not particularly useful for getters or lenses, but given a getter or lens, it returns the referenced value passed through the given function.

views l f s = f (view l s)

review :: Grate s t a b -> b -> t
review :: Reviewer s t a b -> b -> t