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]