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GHC 9.14.1 · lts/ghc-9.14.x · 6d5fdfd · 2026-10-12

Modulelens-5.3.6Haskell2010

Control.Lens.Internal.Fold

Contents

Monoids for folding
Semigroups for folding

Synopsis

newtype Folding
newtype Traversed
newtype TraversedF
newtype Sequenced
data Leftmost
value getLeftmost
data Rightmost
value getRightmost
data ReifiedMonoid
newtype NonEmptyDList

Packagelens-5.3.6
Exports10
LanguageHaskell2010
LicenceBSD-2-Clause
SourceFold.hs

Monoids for folding

newtypenewtype Folding (f :: Type -> Type) a

A Monoid for a Contravariant Applicative.

Constructors

Folding
- getFolding :: f a

Instances2Semigroup, Monoid

(Contravariant f, Applicative f) => Semigroup (Folding f a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
(Contravariant f, Applicative f) => Monoid (Folding f a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

newtypenewtype Traversed a (f :: Type -> Type)

Used internally by Control.Lens.Traversal.traverseOf_ and the like.

The argument a of the result should not be used!

Constructors

Traversed
- getTraversed :: f a

Instances2Semigroup, Monoid

Applicative f => Semigroup (Traversed a f)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
Applicative f => Monoid (Traversed a f)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

newtypenewtype TraversedF a (f :: Type -> Type)

Used internally by traverse1Of_ and the like.

Constructors

TraversedF
- getTraversedF :: f a

Instances2Semigroup, Monoid

Apply f => Semigroup (TraversedF a f)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
(Apply f, Applicative f) => Monoid (TraversedF a f)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

newtypenewtype Sequenced a (m :: Type -> Type)

Used internally by Control.Lens.Traversal.mapM_ and the like.

The argument a of the result should not be used!

See 4.16 Changelog entry for the explanation of "why not Apply f =>"?

Constructors

Sequenced
- getSequenced :: m a

Instances2Semigroup, Monoid

Monad m => Semigroup (Sequenced a m)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
Monad m => Monoid (Sequenced a m)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

datadata Leftmost a

Used for firstOf.

Constructors

LPure
LLeaf a
LStep (Leftmost a)

Instances2Semigroup, Monoid

Semigroup (Leftmost a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
Monoid (Leftmost a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

valuegetLeftmost :: Leftmost a -> Maybe a

Extract the Leftmost element. This will fairly eagerly determine that it can return Just the moment it sees any element at all.

datadata Rightmost a

Used for lastOf.

Constructors

RPure
RLeaf a
RStep (Rightmost a)

Instances2Semigroup, Monoid

Semigroup (Rightmost a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold
Monoid (Rightmost a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold

valuegetRightmost :: Rightmost a -> Maybe a

Extract the Rightmost element. This will fairly eagerly determine that it can return Just the moment it sees any element at all.

datadata ReifiedMonoid a

Constructors

ReifiedMonoid
- reifiedMappend :: a -> a -> a
- reifiedMempty :: a

Semigroups for folding

newtypenewtype NonEmptyDList a

Constructors

NonEmptyDList
- getNonEmptyDList :: [a] -> NonEmpty a

Instances1Semigroup

Semigroup (NonEmptyDList a)Defined in lens-5.3.6 · Control.Lens.Internal.Fold