Data.Sequence.Lens

Documentation

viewL :: Iso (Seq a) (Seq b) (ViewL a) (ViewL b)

A Seq is isomorphic to a ViewL

viewl m ≡ m ^. viewL

>>> Seq.fromList [a,b,c] ^. viewL
a :< fromList [b,c]

>>> Seq.empty ^. viewL
EmptyL

>>> EmptyL ^. from viewL
fromList []

>>> review viewL $ a :< fromList [b,c]
fromList [a,b,c]

viewR :: Iso (Seq a) (Seq b) (ViewR a) (ViewR b)

A Seq is isomorphic to a ViewR

viewr m ≡ m ^. viewR

>>> Seq.fromList [a,b,c] ^. viewR
fromList [a,b] :> c

>>> Seq.empty ^. viewR
EmptyR

>>> EmptyR ^. from viewR
fromList []

>>> review viewR $ fromList [a,b] :> c
fromList [a,b,c]

sliced :: Int -> Int -> IndexedTraversal' Int (Seq a) a

Traverse all the elements numbered from i to j of a Seq

>>> fromList [a,b,c,d,e] & sliced 1 3 %~ f
fromList [a,f b,f c,d,e]

slicedTo :: Int -> IndexedTraversal' Int (Seq a) a

Traverse the first n elements of a Seq

>>> fromList [a,b,c,d,e] ^.. slicedTo 2
[a,b]

>>> fromList [a,b,c,d,e] & slicedTo 2 %~ f
fromList [f a,f b,c,d,e]

>>> fromList [a,b,c,d,e] & slicedTo 10 .~ x
fromList [x,x,x,x,x]

slicedFrom :: Int -> IndexedTraversal' Int (Seq a) a

Traverse all but the first n elements of a Seq

>>> fromList [a,b,c,d,e] ^.. slicedFrom 2
[c,d,e]

>>> fromList [a,b,c,d,e] & slicedFrom 2 %~ f
fromList [a,b,f c,f d,f e]

>>> fromList [a,b,c,d,e] & slicedFrom 10 .~ x
fromList [a,b,c,d,e]

seqOf :: Getting (Seq a) s a -> s -> Seq a

Construct a Seq from a Getter, Fold, Traversal, Lens or Iso.

>>> seqOf folded ["hello","world"]
fromList ["hello","world"]

>>> seqOf (folded._2) [("hello",1),("world",2),("!!!",3)]
fromList [1,2,3]

seqOf :: Getter s a     -> s -> Seq a
seqOf :: Fold s a       -> s -> Seq a
seqOf :: Iso' s a       -> s -> Seq a
seqOf :: Lens' s a      -> s -> Seq a
seqOf :: Traversal' s a -> s -> Seq a