Haskell Hierarchical Libraries (base package)ContentsIndex
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
Functor Seq
Foldable Seq
Traversable Seq
Monad Seq
MonadPlus Seq
Eq a => Eq (Seq a)
Ord a => Ord (Seq a)
Show a => Show (Seq a)
Read a => Read (Seq a)
Monoid (Seq a)
Typeable1 Seq
Data a => Data (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
EmptyLempty sequence
(:<) a (Seq a)leftmost element and the rest of the sequence
Instances
Eq a => Eq (ViewL a)
Ord a => Ord (ViewL a)
Show a => Show (ViewL a)
Read a => Read (ViewL a)
Data a => Data (ViewL a)
Typeable1 ViewL
Functor ViewL
Foldable ViewL
Traversable ViewL
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
EmptyRempty sequence
(:>) (Seq a) athe sequence minus the rightmost element, and the rightmost element
Instances
Eq a => Eq (ViewR a)
Ord a => Ord (ViewR a)
Show a => Show (ViewR a)
Read a => Read (ViewR a)
Data a => Data (ViewR a)
Typeable1 ViewR
Functor ViewR
Foldable ViewR
Traversable ViewR
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.
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