Data.Sequence
 Portability portable Stability experimental Maintainer ross@soi.city.ac.uk
 Contents Construction Deconstruction Queries Views Indexing Transformations
Description

General purpose finite sequences. Apart from being finite and having strict operations, sequences also differ from lists in supporting a wider variety of operations efficiently.

An amortized running time is given for each operation, with n referring to the length of the sequence and i being the integral index used by some operations. These bounds hold even in a persistent (shared) setting.

The implementation uses 2-3 finger trees annotated with sizes, as described in section 4.2 of

Note: Many of these operations have the same names as similar operations on lists in the Prelude. The ambiguity may be resolved using either qualification or the hiding clause.

Synopsis
data Seq a
empty :: Seq a
singleton :: a -> Seq a
(<|) :: a -> Seq a -> Seq a
(|>) :: Seq a -> a -> Seq a
(><) :: Seq a -> Seq a -> Seq a
fromList :: [a] -> Seq a
null :: Seq a -> Bool
length :: Seq a -> Int
data ViewL a
 = EmptyL | (:<) a (Seq a)
viewl :: Seq a -> ViewL a
data ViewR a
 = EmptyR | (:>) (Seq a) a
viewr :: Seq a -> ViewR a
index :: Seq a -> Int -> a
adjust :: (a -> a) -> Int -> Seq a -> Seq a
update :: Int -> a -> Seq a -> Seq a
take :: Int -> Seq a -> Seq a
drop :: Int -> Seq a -> Seq a
splitAt :: Int -> Seq a -> (Seq a, Seq a)
reverse :: Seq a -> Seq a
Documentation
data Seq a
General-purpose finite sequences. Instances
 Foldable Seq Functor Seq Monad Seq MonadPlus Seq Traversable Seq Typeable1 Seq Data a => Data (Seq a) Eq a => Eq (Seq a) Monoid (Seq a) Ord a => Ord (Seq a) Read a => Read (Seq a) Show a => Show (Seq a)
Construction
empty :: Seq a
O(1). The empty sequence.
singleton :: a -> Seq a
O(1). A singleton sequence.
(<|) :: a -> Seq a -> Seq a
O(1). Add an element to the left end of a sequence. Mnemonic: a triangle with the single element at the pointy end.
(|>) :: Seq a -> a -> Seq a
O(1). Add an element to the right end of a sequence. Mnemonic: a triangle with the single element at the pointy end.
(><) :: Seq a -> Seq a -> Seq a
O(log(min(n1,n2))). Concatenate two sequences.
fromList :: [a] -> Seq a
O(n). Create a sequence from a finite list of elements.
Deconstruction
Queries
null :: Seq a -> Bool
O(1). Is this the empty sequence?
length :: Seq a -> Int
O(1). The number of elements in the sequence.
Views
data ViewL a
View of the left end of a sequence.
Constructors
 EmptyL empty sequence (:<) a (Seq a) leftmost element and the rest of the sequence Instances
 Foldable ViewL Functor ViewL Traversable ViewL Typeable1 ViewL Data a => Data (ViewL a) Eq a => Eq (ViewL a) Ord a => Ord (ViewL a) Read a => Read (ViewL a) Show a => Show (ViewL a)
viewl :: Seq a -> ViewL a
O(1). Analyse the left end of a sequence.
data ViewR a
View of the right end of a sequence.
Constructors
 EmptyR empty sequence (:>) (Seq a) a the sequence minus the rightmost element, and the rightmost element Instances
 Foldable ViewR Functor ViewR Traversable ViewR Typeable1 ViewR Data a => Data (ViewR a) Eq a => Eq (ViewR a) Ord a => Ord (ViewR a) Read a => Read (ViewR a) Show a => Show (ViewR a)
viewr :: Seq a -> ViewR a
O(1). Analyse the right end of a sequence.
Indexing
index :: Seq a -> Int -> a
O(log(min(i,n-i))). The element at the specified position
adjust :: (a -> a) -> Int -> Seq a -> Seq a
O(log(min(i,n-i))). Update the element at the specified position
update :: Int -> a -> Seq a -> Seq a
O(log(min(i,n-i))). Replace the element at the specified position
take :: Int -> Seq a -> Seq a
O(log(min(i,n-i))). The first i elements of a sequence.
drop :: Int -> Seq a -> Seq a
O(log(min(i,n-i))). Elements of a sequence after the first i.
splitAt :: Int -> Seq a -> (Seq a, Seq a)
O(log(min(i,n-i))). Split a sequence at a given position.
Transformations
reverse :: Seq a -> Seq a
O(n). The reverse of a sequence.