lens-4.2: Lenses, Folds and Traversals

Copyright(C) 2012-2014 Edward Kmett
LicenseBSD-style (see the file LICENSE)
MaintainerEdward Kmett <ekmett@gmail.com>
Stabilityexperimental
Portabilitynon-portable
Safe HaskellTrustworthy
LanguageHaskell98

Control.Lens.Internal.Fold

Contents

Description

 

Synopsis

Monoids for folding

newtype Folding f a Source

Constructors

Folding 

Fields

getFolding :: f a
 

Instances

newtype Traversed a f Source

Used internally by traverseOf_ and the like.

The argument a of the result should not be used!

Constructors

Traversed 

Fields

getTraversed :: f a
 

Instances

newtype Sequenced a m Source

Used internally by mapM_ and the like.

The argument a of the result should not be used!

Constructors

Sequenced 

Fields

getSequenced :: m a
 

Instances

Monad m => Monoid (Sequenced a m) 
Apply m => Semigroup (Sequenced a m) 

data Max a Source

Used for maximumOf.

Constructors

NoMax 
Max a 

Instances

Ord a => Monoid (Max a) 
Ord a => Semigroup (Max a) 

getMax :: Max a -> Maybe a Source

Obtain the maximum.

data Min a Source

Used for minimumOf.

Constructors

NoMin 
Min a 

Instances

Ord a => Monoid (Min a) 
Ord a => Semigroup (Min a) 

getMin :: Min a -> Maybe a Source

Obtain the minimum.

data Leftmost a Source

Used for preview.

Constructors

LPure 
LLeaf a 
LStep (Leftmost a) 

Instances

getLeftmost :: Leftmost a -> Maybe a Source

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

data Rightmost a Source

Used for lastOf.

Constructors

RPure 
RLeaf a 
RStep (Rightmost a) 

Instances

getRightmost :: Rightmost a -> Maybe a Source

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

data ReifiedMonoid a Source

Constructors

ReifiedMonoid 

Fields

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

newtype M a s Source

Constructors

M a 

Instances

Reifies * s (ReifiedMonoid a) => Monoid (M a s) 

reifyFold :: (a -> a -> a) -> a -> (forall s. Reifies s (ReifiedMonoid a) => t -> M a s) -> t -> a Source