Safe Haskell  SafeInferred 

Language  Haskell2010 
Seq
. Import as:
import qualified RIO.Seq as Seq
Synopsis
 data Seq a where
 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
 fromFunction :: Int > (Int > a) > Seq a
 fromArray :: Ix i => Array i a > Seq a
 replicate :: Int > a > Seq a
 replicateA :: Applicative f => Int > f a > f (Seq a)
 replicateM :: Applicative m => Int > m a > m (Seq a)
 cycleTaking :: Int > Seq a > Seq a
 iterateN :: Int > (a > a) > a > Seq a
 unfoldr :: (b > Maybe (a, b)) > b > Seq a
 unfoldl :: (b > Maybe (b, a)) > b > Seq a
 null :: Seq a > Bool
 length :: Seq a > Int
 data ViewL a
 viewl :: Seq a > ViewL a
 data ViewR a
 viewr :: Seq a > ViewR a
 scanl :: (a > b > a) > a > Seq b > Seq a
 scanl1 :: (a > a > a) > Seq a > Seq a
 scanr :: (a > b > b) > b > Seq a > Seq b
 scanr1 :: (a > a > a) > Seq a > Seq a
 tails :: Seq a > Seq (Seq a)
 inits :: Seq a > Seq (Seq a)
 chunksOf :: Int > Seq a > Seq (Seq a)
 takeWhileL :: (a > Bool) > Seq a > Seq a
 takeWhileR :: (a > Bool) > Seq a > Seq a
 dropWhileL :: (a > Bool) > Seq a > Seq a
 dropWhileR :: (a > Bool) > Seq a > Seq a
 spanl :: (a > Bool) > Seq a > (Seq a, Seq a)
 spanr :: (a > Bool) > Seq a > (Seq a, Seq a)
 breakl :: (a > Bool) > Seq a > (Seq a, Seq a)
 breakr :: (a > Bool) > Seq a > (Seq a, Seq a)
 partition :: (a > Bool) > Seq a > (Seq a, Seq a)
 filter :: (a > Bool) > Seq a > Seq a
 sort :: Ord a => Seq a > Seq a
 sortBy :: (a > a > Ordering) > Seq a > Seq a
 unstableSort :: Ord a => Seq a > Seq a
 unstableSortBy :: (a > a > Ordering) > Seq a > Seq a
 lookup :: Int > Seq a > Maybe a
 (!?) :: Seq a > Int > Maybe a
 index :: Seq a > Int > a
 adjust :: (a > a) > Int > Seq a > Seq 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
 insertAt :: Int > a > Seq a > Seq a
 deleteAt :: Int > Seq a > Seq a
 splitAt :: Int > Seq a > (Seq a, Seq a)
 elemIndexL :: Eq a => a > Seq a > Maybe Int
 elemIndicesL :: Eq a => a > Seq a > [Int]
 elemIndexR :: Eq a => a > Seq a > Maybe Int
 elemIndicesR :: Eq a => a > Seq a > [Int]
 findIndexL :: (a > Bool) > Seq a > Maybe Int
 findIndicesL :: (a > Bool) > Seq a > [Int]
 findIndexR :: (a > Bool) > Seq a > Maybe Int
 findIndicesR :: (a > Bool) > Seq a > [Int]
 foldMapWithIndex :: Monoid m => (Int > a > m) > Seq a > m
 foldlWithIndex :: (b > Int > a > b) > b > Seq a > b
 foldrWithIndex :: (Int > a > b > b) > b > Seq a > b
 mapWithIndex :: (Int > a > b) > Seq a > Seq b
 traverseWithIndex :: Applicative f => (Int > a > f b) > Seq a > f (Seq b)
 reverse :: Seq a > Seq a
 intersperse :: a > Seq a > Seq a
 zip :: Seq a > Seq b > Seq (a, b)
 zipWith :: (a > b > c) > Seq a > Seq b > Seq c
 zip3 :: Seq a > Seq b > Seq c > Seq (a, b, c)
 zipWith3 :: (a > b > c > d) > Seq a > Seq b > Seq c > Seq d
 zip4 :: Seq a > Seq b > Seq c > Seq d > Seq (a, b, c, d)
 zipWith4 :: (a > b > c > d > e) > Seq a > Seq b > Seq c > Seq d > Seq e
Documentation
Generalpurpose finite sequences.
pattern Empty :: Seq a  A bidirectional pattern synonym matching an empty sequence. Since: containers0.5.8 
pattern (:>) :: Seq a > a > Seq a infixl 5  A bidirectional pattern synonym viewing the rear of a nonempty sequence. Since: containers0.5.8 
pattern (:<) :: a > Seq a > Seq a infixr 5  A bidirectional pattern synonym viewing the front of a nonempty sequence. Since: containers0.5.8 
Instances
Monad Seq  
Functor Seq  
MonadFix Seq  Since: containers0.5.11 
Defined in Data.Sequence.Internal  
Applicative Seq  Since: containers0.5.4 
Foldable Seq  
Defined in Data.Sequence.Internal fold :: Monoid m => Seq m > m # foldMap :: Monoid m => (a > m) > Seq a > m # foldMap' :: Monoid m => (a > m) > Seq a > m # foldr :: (a > b > b) > b > Seq a > b # foldr' :: (a > b > b) > b > Seq a > b # foldl :: (b > a > b) > b > Seq a > b # foldl' :: (b > a > b) > b > Seq a > b # foldr1 :: (a > a > a) > Seq a > a # foldl1 :: (a > a > a) > Seq a > a # elem :: Eq a => a > Seq a > Bool # maximum :: Ord a => Seq a > a #  
Traversable Seq  
Eq1 Seq  Since: containers0.5.9 
Ord1 Seq  Since: containers0.5.9 
Defined in Data.Sequence.Internal  
Read1 Seq  Since: containers0.5.9 
Defined in Data.Sequence.Internal  
Show1 Seq  Since: containers0.5.9 
MonadZip Seq 

Alternative Seq  Since: containers0.5.4 
MonadPlus Seq  
Hashable1 Seq  Since: hashable1.3.4.0 
Defined in Data.Hashable.Class  
UnzipWith Seq  
Defined in Data.Sequence.Internal unzipWith' :: (x > (a, b)) > Seq x > (Seq a, Seq b)  
IsList (Seq a)  
Eq a => Eq (Seq a)  
Data a => Data (Seq a)  
Defined in Data.Sequence.Internal gfoldl :: (forall d b. Data d => c (d > b) > d > c b) > (forall g. g > c g) > Seq a > c (Seq a) # gunfold :: (forall b r. Data b => c (b > r) > c r) > (forall r. r > c r) > Constr > c (Seq a) # dataTypeOf :: Seq a > DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) > Maybe (c (Seq a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) > Maybe (c (Seq a)) # gmapT :: (forall b. Data b => b > b) > Seq a > Seq a # gmapQl :: (r > r' > r) > r > (forall d. Data d => d > r') > Seq a > r # gmapQr :: forall r r'. (r' > r > r) > r > (forall d. Data d => d > r') > Seq a > r # gmapQ :: (forall d. Data d => d > u) > Seq a > [u] # gmapQi :: Int > (forall d. Data d => d > u) > Seq a > u # gmapM :: Monad m => (forall d. Data d => d > m d) > Seq a > m (Seq a) # gmapMp :: MonadPlus m => (forall d. Data d => d > m d) > Seq a > m (Seq a) # gmapMo :: MonadPlus m => (forall d. Data d => d > m d) > Seq a > m (Seq a) #  
Ord a => Ord (Seq a)  
Read a => Read (Seq a)  
Show a => Show (Seq a)  
a ~ Char => IsString (Seq a)  Since: containers0.5.7 
Defined in Data.Sequence.Internal fromString :: String > Seq a #  
Semigroup (Seq a)  Since: containers0.5.7 
Monoid (Seq a)  
NFData a => NFData (Seq a)  
Defined in Data.Sequence.Internal  
Hashable v => Hashable (Seq v)  Since: hashable1.3.4.0 
Defined in Data.Hashable.Class  
type Item (Seq a)  
Defined in Data.Sequence.Internal 
Construction
(<) :: a > Seq a > Seq a infixr 5 #
\( O(1) \). 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 infixl 5 #
\( O(1) \). Add an element to the right end of a sequence. Mnemonic: a triangle with the single element at the pointy end.
fromFunction :: Int > (Int > a) > Seq a #
\( O(n) \). Convert a given sequence length and a function representing that sequence into a sequence.
Since: containers0.5.6.2
fromArray :: Ix i => Array i a > Seq a #
\( O(n) \). Create a sequence consisting of the elements of an Array
.
Note that the resulting sequence elements may be evaluated lazily (as on GHC),
so you must force the entire structure to be sure that the original array
can be garbagecollected.
Since: containers0.5.6.2
Repetition
replicate :: Int > a > Seq a #
\( O(\log n) \). replicate n x
is a sequence consisting of n
copies of x
.
replicateA :: Applicative f => Int > f a > f (Seq a) #
replicateA
is an Applicative
version of replicate
, and makes
\( O(\log n) \) calls to liftA2
and pure
.
replicateA n x = sequenceA (replicate n x)
replicateM :: Applicative m => Int > m a > m (Seq a) #
replicateM
is a sequence counterpart of replicateM
.
replicateM n x = sequence (replicate n x)
For base >= 4.8.0
and containers >= 0.5.11
, replicateM
is a synonym for replicateA
.
cycleTaking :: Int > Seq a > Seq a #
O(log k).
forms a sequence of length cycleTaking
k xsk
by
repeatedly concatenating xs
with itself. xs
may only be empty if
k
is 0.
cycleTaking k = fromList . take k . cycle . toList
Iterative construction
iterateN :: Int > (a > a) > a > Seq a #
\( O(n) \). Constructs a sequence by repeated application of a function to a seed value.
iterateN n f x = fromList (Prelude.take n (Prelude.iterate f x))
unfoldr :: (b > Maybe (a, b)) > b > Seq a #
Builds a sequence from a seed value. Takes time linear in the number of generated elements. WARNING: If the number of generated elements is infinite, this method will not terminate.
Deconstruction
Additional functions for deconstructing sequences are available via the
Foldable
instance of Seq
.
Queries
Views
View of the left end of a sequence.
Instances
Functor ViewL  
Foldable ViewL  
Defined in Data.Sequence.Internal fold :: Monoid m => ViewL m > m # foldMap :: Monoid m => (a > m) > ViewL a > m # foldMap' :: Monoid m => (a > m) > ViewL a > m # foldr :: (a > b > b) > b > ViewL a > b # foldr' :: (a > b > b) > b > ViewL a > b # foldl :: (b > a > b) > b > ViewL a > b # foldl' :: (b > a > b) > b > ViewL a > b # foldr1 :: (a > a > a) > ViewL a > a # foldl1 :: (a > a > a) > ViewL a > a # elem :: Eq a => a > ViewL a > Bool # maximum :: Ord a => ViewL a > a # minimum :: Ord a => ViewL a > a #  
Traversable ViewL  
Eq a => Eq (ViewL a)  
Data a => Data (ViewL a)  
Defined in Data.Sequence.Internal gfoldl :: (forall d b. Data d => c (d > b) > d > c b) > (forall g. g > c g) > ViewL a > c (ViewL a) # gunfold :: (forall b r. Data b => c (b > r) > c r) > (forall r. r > c r) > Constr > c (ViewL a) # toConstr :: ViewL a > Constr # dataTypeOf :: ViewL a > DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) > Maybe (c (ViewL a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) > Maybe (c (ViewL a)) # gmapT :: (forall b. Data b => b > b) > ViewL a > ViewL a # gmapQl :: (r > r' > r) > r > (forall d. Data d => d > r') > ViewL a > r # gmapQr :: forall r r'. (r' > r > r) > r > (forall d. Data d => d > r') > ViewL a > r # gmapQ :: (forall d. Data d => d > u) > ViewL a > [u] # gmapQi :: Int > (forall d. Data d => d > u) > ViewL a > u # gmapM :: Monad m => (forall d. Data d => d > m d) > ViewL a > m (ViewL a) # gmapMp :: MonadPlus m => (forall d. Data d => d > m d) > ViewL a > m (ViewL a) # gmapMo :: MonadPlus m => (forall d. Data d => d > m d) > ViewL a > m (ViewL a) #  
Ord a => Ord (ViewL a)  
Read a => Read (ViewL a)  
Show a => Show (ViewL a)  
Generic (ViewL a)  Since: containers0.5.8 
Generic1 ViewL  Since: containers0.5.8 
type Rep (ViewL a)  
Defined in Data.Sequence.Internal type Rep (ViewL a) = D1 ('MetaData "ViewL" "Data.Sequence.Internal" "containers0.6.2.1" 'False) (C1 ('MetaCons "EmptyL" 'PrefixI 'False) (U1 :: Type > Type) :+: C1 ('MetaCons ":<" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (Seq a))))  
type Rep1 ViewL  
Defined in Data.Sequence.Internal type Rep1 ViewL = D1 ('MetaData "ViewL" "Data.Sequence.Internal" "containers0.6.2.1" 'False) (C1 ('MetaCons "EmptyL" 'PrefixI 'False) (U1 :: Type > Type) :+: C1 ('MetaCons ":<" ('InfixI 'RightAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1 :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 Seq))) 
View of the right end of a sequence.
EmptyR  empty sequence 
(Seq a) :> a infixl 5  the sequence minus the rightmost element, and the rightmost element 
Instances
Functor ViewR  
Foldable ViewR  
Defined in Data.Sequence.Internal fold :: Monoid m => ViewR m > m # foldMap :: Monoid m => (a > m) > ViewR a > m # foldMap' :: Monoid m => (a > m) > ViewR a > m # foldr :: (a > b > b) > b > ViewR a > b # foldr' :: (a > b > b) > b > ViewR a > b # foldl :: (b > a > b) > b > ViewR a > b # foldl' :: (b > a > b) > b > ViewR a > b # foldr1 :: (a > a > a) > ViewR a > a # foldl1 :: (a > a > a) > ViewR a > a # elem :: Eq a => a > ViewR a > Bool # maximum :: Ord a => ViewR a > a # minimum :: Ord a => ViewR a > a #  
Traversable ViewR  
Eq a => Eq (ViewR a)  
Data a => Data (ViewR a)  
Defined in Data.Sequence.Internal gfoldl :: (forall d b. Data d => c (d > b) > d > c b) > (forall g. g > c g) > ViewR a > c (ViewR a) # gunfold :: (forall b r. Data b => c (b > r) > c r) > (forall r. r > c r) > Constr > c (ViewR a) # toConstr :: ViewR a > Constr # dataTypeOf :: ViewR a > DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) > Maybe (c (ViewR a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) > Maybe (c (ViewR a)) # gmapT :: (forall b. Data b => b > b) > ViewR a > ViewR a # gmapQl :: (r > r' > r) > r > (forall d. Data d => d > r') > ViewR a > r # gmapQr :: forall r r'. (r' > r > r) > r > (forall d. Data d => d > r') > ViewR a > r # gmapQ :: (forall d. Data d => d > u) > ViewR a > [u] # gmapQi :: Int > (forall d. Data d => d > u) > ViewR a > u # gmapM :: Monad m => (forall d. Data d => d > m d) > ViewR a > m (ViewR a) # gmapMp :: MonadPlus m => (forall d. Data d => d > m d) > ViewR a > m (ViewR a) # gmapMo :: MonadPlus m => (forall d. Data d => d > m d) > ViewR a > m (ViewR a) #  
Ord a => Ord (ViewR a)  
Read a => Read (ViewR a)  
Show a => Show (ViewR a)  
Generic (ViewR a)  Since: containers0.5.8 
Generic1 ViewR  Since: containers0.5.8 
type Rep (ViewR a)  
Defined in Data.Sequence.Internal type Rep (ViewR a) = D1 ('MetaData "ViewR" "Data.Sequence.Internal" "containers0.6.2.1" 'False) (C1 ('MetaCons "EmptyR" 'PrefixI 'False) (U1 :: Type > Type) :+: C1 ('MetaCons ":>" ('InfixI 'LeftAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (Seq a)) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))  
type Rep1 ViewR  
Defined in Data.Sequence.Internal type Rep1 ViewR = D1 ('MetaData "ViewR" "Data.Sequence.Internal" "containers0.6.2.1" 'False) (C1 ('MetaCons "EmptyR" 'PrefixI 'False) (U1 :: Type > Type) :+: C1 ('MetaCons ":>" ('InfixI 'LeftAssociative 5) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 Seq) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1)) 
Scans
Sublists
tails :: Seq a > Seq (Seq a) #
\( O(n) \). Returns a sequence of all suffixes of this sequence, longest first. For example,
tails (fromList "abc") = fromList [fromList "abc", fromList "bc", fromList "c", fromList ""]
Evaluating the \( i \)th suffix takes \( O(\log(\min(i, ni))) \), but evaluating every suffix in the sequence takes \( O(n) \) due to sharing.
inits :: Seq a > Seq (Seq a) #
\( O(n) \). Returns a sequence of all prefixes of this sequence, shortest first. For example,
inits (fromList "abc") = fromList [fromList "", fromList "a", fromList "ab", fromList "abc"]
Evaluating the \( i \)th prefix takes \( O(\log(\min(i, ni))) \), but evaluating every prefix in the sequence takes \( O(n) \) due to sharing.
chunksOf :: Int > Seq a > Seq (Seq a) #
\(O \Bigl(\bigl(\frac{n}{c}\bigr) \log c\Bigr)\). chunksOf c xs
splits xs
into chunks of size c>0
.
If c
does not divide the length of xs
evenly, then the last element
of the result will be short.
Side note: the given performance bound is missing some messy terms that only really affect edge cases. Performance degrades smoothly from \( O(1) \) (for \( c = n \)) to \( O(n) \) (for \( c = 1 \)). The true bound is more like \( O \Bigl( \bigl(\frac{n}{c}  1\bigr) (\log (c + 1)) + 1 \Bigr) \)
Since: containers0.5.8
Sequential searches
takeWhileL :: (a > Bool) > Seq a > Seq a #
\( O(i) \) where \( i \) is the prefix length. takeWhileL
, applied
to a predicate p
and a sequence xs
, returns the longest prefix
(possibly empty) of xs
of elements that satisfy p
.
takeWhileR :: (a > Bool) > Seq a > Seq a #
\( O(i) \) where \( i \) is the suffix length. takeWhileR
, applied
to a predicate p
and a sequence xs
, returns the longest suffix
(possibly empty) of xs
of elements that satisfy p
.
is equivalent to takeWhileR
p xs
.reverse
(takeWhileL
p (reverse
xs))
dropWhileL :: (a > Bool) > Seq a > Seq a #
\( O(i) \) where \( i \) is the prefix length.
returns
the suffix remaining after dropWhileL
p xs
.takeWhileL
p xs
dropWhileR :: (a > Bool) > Seq a > Seq a #
\( O(i) \) where \( i \) is the suffix length.
returns
the prefix remaining after dropWhileR
p xs
.takeWhileR
p xs
is equivalent to dropWhileR
p xs
.reverse
(dropWhileL
p (reverse
xs))
spanl :: (a > Bool) > Seq a > (Seq a, Seq a) #
\( O(i) \) where \( i \) is the prefix length. spanl
, applied to
a predicate p
and a sequence xs
, returns a pair whose first
element is the longest prefix (possibly empty) of xs
of elements that
satisfy p
and the second element is the remainder of the sequence.
spanr :: (a > Bool) > Seq a > (Seq a, Seq a) #
\( O(i) \) where \( i \) is the suffix length. spanr
, applied to a
predicate p
and a sequence xs
, returns a pair whose first element
is the longest suffix (possibly empty) of xs
of elements that
satisfy p
and the second element is the remainder of the sequence.
breakl :: (a > Bool) > Seq a > (Seq a, Seq a) #
\( O(i) \) where \( i \) is the breakpoint index. breakl
, applied to a
predicate p
and a sequence xs
, returns a pair whose first element
is the longest prefix (possibly empty) of xs
of elements that
do not satisfy p
and the second element is the remainder of
the sequence.
partition :: (a > Bool) > Seq a > (Seq a, Seq a) #
\( O(n) \). The partition
function takes a predicate p
and a
sequence xs
and returns sequences of those elements which do and
do not satisfy the predicate.
filter :: (a > Bool) > Seq a > Seq a #
\( O(n) \). The filter
function takes a predicate p
and a sequence
xs
and returns a sequence of those elements which satisfy the
predicate.
Sorting
sort :: Ord a => Seq a > Seq a #
\( O(n \log n) \). sort
sorts the specified Seq
by the natural
ordering of its elements. The sort is stable. If stability is not
required, unstableSort
can be slightly faster.
Since: containers0.3.0
sortBy :: (a > a > Ordering) > Seq a > Seq a #
\( O(n \log n) \). sortBy
sorts the specified Seq
according to the
specified comparator. The sort is stable. If stability is not required,
unstableSortBy
can be slightly faster.
Since: containers0.3.0
unstableSort :: Ord a => Seq a > Seq a #
\( O(n \log n) \). unstableSort
sorts the specified Seq
by
the natural ordering of its elements, but the sort is not stable.
This algorithm is frequently faster and uses less memory than sort
.
unstableSortBy :: (a > a > Ordering) > Seq a > Seq a #
\( O(n \log n) \). A generalization of unstableSort
, unstableSortBy
takes an arbitrary comparator and sorts the specified sequence.
The sort is not stable. This algorithm is frequently faster and
uses less memory than sortBy
.
Since: containers0.3.0
Indexing
lookup :: Int > Seq a > Maybe a #
\( O(\log(\min(i,ni))) \). The element at the specified position,
counting from 0. If the specified position is negative or at
least the length of the sequence, lookup
returns Nothing
.
0 <= i < length xs ==> lookup i xs == Just (toList xs !! i)
i < 0  i >= length xs ==> lookup i xs = Nothing
Unlike index
, this can be used to retrieve an element without
forcing it. For example, to insert the fifth element of a sequence
xs
into a Map
m
at key k
, you could use
case lookup 5 xs of
Nothing > m
Just x > insert
k x m
Since: containers0.5.8
(!?) :: Seq a > Int > Maybe a #
\( O(\log(\min(i,ni))) \). A flipped, infix version of lookup
.
Since: containers0.5.8
\( O(\log(\min(i,ni))) \). The element at the specified position,
counting from 0. The argument should thus be a nonnegative
integer less than the size of the sequence.
If the position is out of range, index
fails with an error.
xs `index` i = toList xs !! i
Caution: index
necessarily delays retrieving the requested
element until the result is forced. It can therefore lead to a space
leak if the result is stored, unforced, in another structure. To retrieve
an element immediately without forcing it, use lookup
or (!?)
.
adjust :: (a > a) > Int > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). Update the element at the specified position. If
the position is out of range, the original sequence is returned. adjust
can lead to poor performance and even memory leaks, because it does not
force the new value before installing it in the sequence. adjust'
should
usually be preferred.
Since: containers0.5.8
adjust' :: (a > a) > Int > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). Update the element at the specified position. If the position is out of range, the original sequence is returned. The new value is forced before it is installed in the sequence.
adjust' f i xs = case xs !? i of Nothing > xs Just x > let !x' = f x in update i x' xs
Since: containers0.5.8
update :: Int > a > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). Replace the element at the specified position. If the position is out of range, the original sequence is returned.
take :: Int > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). The first i
elements of a sequence.
If i
is negative,
yields the empty sequence.
If the sequence contains fewer than take
i si
elements, the whole sequence
is returned.
drop :: Int > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). Elements of a sequence after the first i
.
If i
is negative,
yields the whole sequence.
If the sequence contains fewer than drop
i si
elements, the empty sequence
is returned.
insertAt :: Int > a > Seq a > Seq a #
\( O(\log(\min(i,ni))) \).
inserts insertAt
i x xsx
into xs
at the index i
, shifting the rest of the sequence over.
insertAt 2 x (fromList [a,b,c,d]) = fromList [a,b,x,c,d] insertAt 4 x (fromList [a,b,c,d]) = insertAt 10 x (fromList [a,b,c,d]) = fromList [a,b,c,d,x]
insertAt i x xs = take i xs >< singleton x >< drop i xs
Since: containers0.5.8
deleteAt :: Int > Seq a > Seq a #
\( O(\log(\min(i,ni))) \). Delete the element of a sequence at a given index. Return the original sequence if the index is out of range.
deleteAt 2 [a,b,c,d] = [a,b,d] deleteAt 4 [a,b,c,d] = deleteAt (1) [a,b,c,d] = [a,b,c,d]
Since: containers0.5.8
Indexing with predicates
These functions perform sequential searches from the left or right ends of the sequence elements.
elemIndexL :: Eq a => a > Seq a > Maybe Int #
elemIndexL
finds the leftmost index of the specified element,
if it is present, and otherwise Nothing
.
elemIndicesL :: Eq a => a > Seq a > [Int] #
elemIndicesL
finds the indices of the specified element, from
left to right (i.e. in ascending order).
elemIndexR :: Eq a => a > Seq a > Maybe Int #
elemIndexR
finds the rightmost index of the specified element,
if it is present, and otherwise Nothing
.
elemIndicesR :: Eq a => a > Seq a > [Int] #
elemIndicesR
finds the indices of the specified element, from
right to left (i.e. in descending order).
findIndexL :: (a > Bool) > Seq a > Maybe Int #
finds the index of the leftmost element that
satisfies findIndexL
p xsp
, if any exist.
findIndicesL :: (a > Bool) > Seq a > [Int] #
finds all indices of elements that satisfy findIndicesL
pp
,
in ascending order.
findIndexR :: (a > Bool) > Seq a > Maybe Int #
finds the index of the rightmost element that
satisfies findIndexR
p xsp
, if any exist.
findIndicesR :: (a > Bool) > Seq a > [Int] #
finds all indices of elements that satisfy findIndicesR
pp
,
in descending order.
Folds
General folds are available via the Foldable
instance of Seq
.
foldMapWithIndex :: Monoid m => (Int > a > m) > Seq a > m #
foldlWithIndex :: (b > Int > a > b) > b > Seq a > b #
foldlWithIndex
is a version of foldl
that also provides access
to the index of each element.
foldrWithIndex :: (Int > a > b > b) > b > Seq a > b #
foldrWithIndex
is a version of foldr
that also provides access
to the index of each element.
Transformations
mapWithIndex :: (Int > a > b) > Seq a > Seq b #
A generalization of fmap
, mapWithIndex
takes a mapping
function that also depends on the element's index, and applies it to every
element in the sequence.
traverseWithIndex :: Applicative f => (Int > a > f b) > Seq a > f (Seq b) #
traverseWithIndex
is a version of traverse
that also offers
access to the index of each element.
Since: containers0.5.8
intersperse :: a > Seq a > Seq a #
\( O(n) \). Intersperse an element between the elements of a sequence.
intersperse a empty = empty intersperse a (singleton x) = singleton x intersperse a (fromList [x,y]) = fromList [x,a,y] intersperse a (fromList [x,y,z]) = fromList [x,a,y,a,z]
Since: containers0.5.8
Zips
zip :: Seq a > Seq b > Seq (a, b) #
\( O(\min(n_1,n_2)) \). zip
takes two sequences and returns a sequence
of corresponding pairs. If one input is short, excess elements are
discarded from the right end of the longer sequence.