Scala Library: scala.collection.SeqProxy
scala.collection.SeqProxy
This trait implements a proxy for sequence objects. It forwards all calls to a different sequence object.
- Annotations
- @ deprecated
- Deprecated
- (Since version 2.11.0) Proxying is deprecated due to lack of use and compiler-level support.
- Source
- Version
- 2.8
- Since
- 2.8
Type Members
type Self = Seq[A]
The type implementing this traversable
- Attributes
- protected[this]
- Definition Classes
- TraversableLike
class WithFilter extends FilterMonadic[A, Repr]
A class supporting filtered operations. Instances of this class are returned by
method withFilter
.
- Definition Classes
- TraversableLike
Concrete Value Members From scala.Function1
def compose[A](g: (A) ⇒ Int): (A) ⇒ A
Composes two instances of Function1 in a new Function1, with this function applied last.
- A
- the type to which function
g
can be applied
- the type to which function
- g
- a function A => T1
- returns
- a new function
f
such thatf(x) == apply(g(x))
- a new function
- Definition Classes
- Function1
- Annotations
- @ unspecialized ()
(defined at scala.Function1)
Concrete Value Members From scala.PartialFunction
def andThen[C](k: (A) ⇒ C): PartialFunction[Int, C]
Composes this partial function with a transformation function that gets applied to results of this partial function.
- C
- the result type of the transformation function.
- k
- the transformation function
- returns
- a partial function with the same domain as this partial function, which maps
arguments
x
tok(this(x))
.
- a partial function with the same domain as this partial function, which maps
arguments
- Definition Classes
- PartialFunction → Function1
(defined at scala.PartialFunction)
def applyOrElse[A1 <: Int, B1 >: A](x: A1, default: (A1) ⇒ B1): B1
Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.
Note that expression pf.applyOrElse(x, default)
is equivalent to
except that applyOrElse
method can be implemented more efficiently. For all
partial function literals the compiler generates an applyOrElse
implementation
which avoids double evaluation of pattern matchers and guards. This makes
applyOrElse
the basis for the efficient implementation for many operations
and scenarios, such as:
- combining partial functions into
orElse
/andThen
chains does not lead to excessiveapply
/isDefinedAt
evaluation lift
andunlift
do not evaluate source functions twice on each invocationrunWith
allows efficient imperative-style combining of partial functions with conditionally applied actions
For non-literal partial function classes with nontrivial isDefinedAt
method it
is recommended to override applyOrElse
with custom implementation that avoids
double isDefinedAt
evaluation. This may result in better performance and more
predictable behavior w.r.t. side effects.
- x
- the function argument
- default
- the fallback function
- returns
- the result of this function or fallback function application.
- Definition Classes
- PartialFunction
- Since
- 2.10
(defined at scala.PartialFunction)
def lift: (Int) ⇒ Option[A]
Turns this partial function into a plain function returning an Option
result.
- returns
- a function that takes an argument
x
toSome(this(x))
ifthis
is defined forx
, and toNone
otherwise.
- a function that takes an argument
- Definition Classes
- PartialFunction
- See also
- Function.unlift
(defined at scala.PartialFunction)
def orElse[A1 <: Int, B1 >: A](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
- A1
- the argument type of the fallback function
- B1
- the result type of the fallback function
- that
- the fallback function
- returns
- a partial function which has as domain the union of the domains of this
partial function and
that
. The resulting partial function takesx
tothis(x)
wherethis
is defined, and tothat(x)
where it is not.
- a partial function which has as domain the union of the domains of this
partial function and
- Definition Classes
- PartialFunction
(defined at scala.PartialFunction)
def runWith[U](action: (A) ⇒ U): (Int) ⇒ Boolean
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression pf.runWith(action)(x)
is equivalent to
except that runWith
is implemented via applyOrElse
and thus potentially more
efficient. Using runWith
avoids double evaluation of pattern matchers and
guards for partial function literals.
- action
- the action function
- returns
- a function which maps arguments
x
toisDefinedAt(x)
. The resulting function runsaction(this(x))
wherethis
is defined.
- a function which maps arguments
- Definition Classes
- PartialFunction
- Since
- 2.10
- See also
applyOrElse
.
(defined at scala.PartialFunction)
Concrete Value Members From scala.Proxy
def equals(that: Any): Boolean
Compares the receiver object ( this
) with the argument object ( that
) for
equivalence.
Any implementation of this method should be an equivalence relation :
- It is reflexive: for any instance
x
of typeAny
,x.equals(x)
should returntrue
. - It is symmetric: for any instances
x
andy
of typeAny
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any instances
x
,y
, andz
of typeAny
ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
.
If you override this method, you should verify that your implementation remains
an equivalence relation. Additionally, when overriding this method it is usually
necessary to override hashCode
to ensure that objects which are “equal” (
o1.equals(o2)
returns true
) hash to the same scala.Int. (
o1.hashCode.equals(o2.hashCode)
).
- that
- the object to compare against this object for equality.
- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Proxy → Any
(defined at scala.Proxy)
Concrete Value Members From scala.collection.IterableLike
def canEqual(that: Any): Boolean
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
- that
- The object with which this iterable collection should be compared
- returns
true
, if this iterable collection can possibly equalthat
,false
otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.
- Definition Classes
- IterableLike → Equals
(defined at scala.collection.IterableLike)
Concrete Value Members From scala.collection.IterableProxyLike
def dropRight(n: Int): Seq[A]
Selects all elements except last n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
- The number of elements to take
- returns
- a iterable collection consisting of all elements of this iterable collection
except the last
n
ones, or else the empty iterable collection, if this iterable collection has less thann
elements.
- a iterable collection consisting of all elements of this iterable collection
except the last
- Definition Classes
- IterableProxyLike → IterableLike
(defined at scala.collection.IterableProxyLike)
def grouped(size: Int): Iterator[Seq[A]]
Partitions elements in fixed size iterable collections.
- size
- the number of elements per group
- returns
- An iterator producing iterable collections of size
size
, except the last will be less than sizesize
if the elements don’t divide evenly.
- An iterator producing iterable collections of size
- Definition Classes
- IterableProxyLike → IterableLike
- See also
- scala.collection.Iterator, method
grouped
- scala.collection.Iterator, method
(defined at scala.collection.IterableProxyLike)
def sameElements[B >: A](that: GenIterable[B]): Boolean
[use case]
Checks if the other iterable collection contains the same elements in the same order as this sequence.
Note: will not terminate for infinite-sized collections.
- that
- the collection to compare with.
- returns
true
, if both collections contain the same elements in the same order,false
otherwise.
- Definition Classes
- IterableProxyLike → IterableLike → GenIterableLike
(defined at scala.collection.IterableProxyLike)
def sliding(size: Int): Iterator[Seq[A]]
Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.) “Sliding window” step is 1 by default.
- size
- the number of elements per group
- returns
- An iterator producing iterable collections of size
size
, except the last and the only element will be truncated if there are fewer elements than size.
- An iterator producing iterable collections of size
- Definition Classes
- IterableProxyLike → IterableLike
- See also
- scala.collection.Iterator, method
sliding
- scala.collection.Iterator, method
(defined at scala.collection.IterableProxyLike)
def sliding(size: Int, step: Int): Iterator[Seq[A]]
Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.)
- size
- the number of elements per group
- step
- the distance between the first elements of successive groups
- returns
- An iterator producing iterable collections of size
size
, except the last and the only element will be truncated if there are fewer elements than size.
- An iterator producing iterable collections of size
- Definition Classes
- IterableProxyLike → IterableLike
- See also
- scala.collection.Iterator, method
sliding
- scala.collection.Iterator, method
(defined at scala.collection.IterableProxyLike)
def takeRight(n: Int): Seq[A]
Selects last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
- the number of elements to take
- returns
- a iterable collection consisting only of the last
n
elements of this iterable collection, or else the whole iterable collection, if it has less thann
elements.
- a iterable collection consisting only of the last
- Definition Classes
- IterableProxyLike → IterableLike
(defined at scala.collection.IterableProxyLike)
def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Seq[A], (A1, B), That]): That
[use case]
Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
- B
- the type of the second half of the returned pairs
- that
- The iterable providing the second half of each result pair
- thisElem
- the element to be used to fill up the result if this sequence is shorter
than
that
.
- the element to be used to fill up the result if this sequence is shorter
than
- thatElem
- the element to be used to fill up the result if
that
is shorter than this sequence.
- the element to be used to fill up the result if
- returns
- a new sequence containing pairs consisting of corresponding elements of this
sequence and
that
. The length of the returned collection is the maximum of the lengths of this sequence andthat
. If this sequence is shorter thanthat
,thisElem
values are used to pad the result. Ifthat
is shorter than this sequence,thatElem
values are used to pad the result.
- a new sequence containing pairs consisting of corresponding elements of this
sequence and
- Definition Classes
- IterableProxyLike → IterableLike → GenIterableLike
(defined at scala.collection.IterableProxyLike)
def zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[Seq[A], (A1, B), That]): That
[use case]
Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.
- B
- the type of the second half of the returned pairs
- that
- The iterable providing the second half of each result pair
- returns
- a new sequence containing pairs consisting of corresponding elements of this
sequence and
that
. The length of the returned collection is the minimum of the lengths of this sequence andthat
.
- a new sequence containing pairs consisting of corresponding elements of this
sequence and
- Definition Classes
- IterableProxyLike → IterableLike → GenIterableLike
(defined at scala.collection.IterableProxyLike)
Concrete Value Members From scala.collection.Parallelizable
def par: ParSeq[A]
Returns a parallel implementation of this collection.
For most collection types, this method creates a new parallel collection by
copying all the elements. For these collection, par
takes linear time. Mutable
collections in this category do not produce a mutable parallel collection that
has the same underlying dataset, so changes in one collection will not be
reflected in the other one.
Specific collections (e.g. ParArray
or mutable.ParHashMap
) override this
default behaviour by creating a parallel collection which shares the same
underlying dataset. For these collections, par
takes constant or sublinear
time.
All parallel collections return a reference to themselves.
- returns
- a parallel implementation of this collection
- Definition Classes
- Parallelizable
(defined at scala.collection.Parallelizable)
Concrete Value Members From scala.collection.Seq
def companion: GenericCompanion[Seq]
The factory companion object that builds instances of class Seq
. (or its
Iterable
superclass where class Seq
is not a Seq
.)
- Definition Classes
- Seq → GenSeq → Iterable → GenIterable → Traversable → GenTraversable → GenericTraversableTemplate
(defined at scala.collection.Seq)
Concrete Value Members From scala.collection.SeqLike
def combinations(n: Int): Iterator[Seq[A]]
Iterates over combinations. A combination of length n
is a subsequence of
the original sequence, with the elements taken in order. Thus, "xy"
and
"yy"
are both length-2 combinations of "xyy"
, but "yx"
is not. If there
is more than one way to generate the same subsequence, only one will be
returned.
For example, "xyyy"
has three different ways to generate "xy"
depending on
whether the first, second, or third "y"
is selected. However, since all are
identical, only one will be chosen. Which of the three will be taken is an
implementation detail that is not defined.
- returns
- An Iterator which traverses the possible n-element combinations of this sequence.
- Definition Classes
- SeqLike
Example:
(defined at scala.collection.SeqLike)
def parCombiner: Combiner[A, ParSeq[A]]
The default par
implementation uses the combiner provided by this method to
create a new parallel collection.
- returns
- a combiner for the parallel collection of type
ParRepr
- a combiner for the parallel collection of type
- Attributes
- protected[this]
- Definition Classes
- SeqLike → TraversableLike → Parallelizable
(defined at scala.collection.SeqLike)
def permutations: Iterator[Seq[A]]
Iterates over distinct permutations.
- returns
- An Iterator which traverses the distinct permutations of this sequence.
- Definition Classes
- SeqLike
Example:
(defined at scala.collection.SeqLike)
def toCollection(repr: Seq[A]): Seq[A]
A conversion from collections of type Repr
to Seq
objects. By default this
is implemented as just a cast, but this can be overridden.
- Attributes
- protected[this]
- Definition Classes
- SeqLike → IterableLike → TraversableLike
(defined at scala.collection.SeqLike)
Concrete Value Members From scala.collection.SeqProxyLike
def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
A copy of the sequence with an element prepended.
Note that :-ending operators are right associative (see example). A mnemonic for
+:
vs. :+
is: the COLon goes on the COLlection side.
Also, the original sequence is not modified, so you will want to capture the result.
Example:
- elem
- the prepended element
- returns
- a new sequence consisting of
elem
followed by all elements of this sequence.
- a new sequence consisting of
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
A copy of this sequence with an element appended.
A mnemonic for +:
vs. :+
is: the COLon goes on the COLlection side.
Note: will not terminate for infinite-sized collections.
Example:
- elem
- the appended element
- returns
- a new sequence consisting of all elements of this sequence followed by
elem
.
- a new sequence consisting of all elements of this sequence followed by
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def apply(idx: Int): A
Selects an element by its index in the sequence.
Example:
- idx
- The index to select.
- returns
- the element of this sequence at index
idx
, where0
indicates the first element.
- the element of this sequence at index
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
- Exceptions thrown
- IndexOutOfBoundsException if
idx
does not satisfy0 <= idx < length
.
- IndexOutOfBoundsException if
(defined at scala.collection.SeqProxyLike)
def containsSlice[B](that: GenSeq[B]): Boolean
Tests whether this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
- the sequence to test
- returns
true
if this sequence contains a slice with the same elements asthat
, otherwisefalse
.
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def contains[A1 >: A](elem: A1): Boolean
Tests whether this sequence contains a given value as an element.
Note: may not terminate for infinite-sized collections.
- elem
- the element to test.
- returns
true
if this sequence has an element that is equal (as determined by==
) toelem
,false
otherwise.
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def corresponds[B](that: GenSeq[B])(p: (A, B) ⇒ Boolean): Boolean
Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.
- B
- the type of the elements of
that
- the type of the elements of
- that
- the other sequence
- p
- the test predicate, which relates elements from both sequences
- returns
true
if both sequences have the same length andp(x, y)
istrue
for all corresponding elementsx
of this sequence andy
ofthat
, otherwisefalse
.
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def diff[B >: A](that: GenSeq[B]): Seq[A]
[use case]
Computes the multiset difference between this sequence and another sequence.
Note: will not terminate for infinite-sized collections.
- that
- the sequence of elements to remove
- returns
- a new sequence which contains all elements of this sequence except some of
occurrences of elements that also appear in
that
. If an element valuex
appears n times inthat
, then the first n occurrences ofx
will not form part of the result, but any following occurrences will.
- a new sequence which contains all elements of this sequence except some of
occurrences of elements that also appear in
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def distinct: Seq[A]
Builds a new sequence from this sequence without any duplicate elements.
Note: will not terminate for infinite-sized collections.
- returns
- A new sequence which contains the first occurrence of every element of this sequence.
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def endsWith[B](that: GenSeq[B]): Boolean
Tests whether this sequence ends with the given sequence.
Note: will not terminate for infinite-sized collections.
- that
- the sequence to test
- returns
true
if this sequence hasthat
as a suffix,false
otherwise.
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def indexOf[B >: A](elem: B): Int
[use case]
Finds index of first occurrence of some value in this sequence.
Note: may not terminate for infinite-sized collections.
- elem
- the element value to search for.
- returns
- the index of the first element of this sequence that is equal (as determined
by
==
) toelem
, or-1
, if none exists.
- the index of the first element of this sequence that is equal (as determined
by
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def indexOf[B >: A](elem: B, from: Int): Int
[use case]
Finds index of first occurrence of some value in this sequence after or at some start index.
Note: may not terminate for infinite-sized collections.
- elem
- the element value to search for.
- from
- the start index
- returns
- the index
>= from
of the first element of this sequence that is equal (as determined by==
) toelem
, or-1
, if none exists.
- the index
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def indexOfSlice[B >: A](that: GenSeq[B]): Int
Finds first index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
- the sequence to test
- returns
- the first index such that the elements of this sequence starting at this
index match the elements of sequence
that
, or-1
of no such subsequence exists.
- the first index such that the elements of this sequence starting at this
index match the elements of sequence
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def indexOfSlice[B >: A](that: GenSeq[B], from: Int): Int
Finds first index after or at a start index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
- the sequence to test
- from
- the start index
- returns
- the first index
>= from
such that the elements of this sequence starting at this index match the elements of sequencethat
, or-1
of no such subsequence exists.
- the first index
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def indexWhere(p: (A) ⇒ Boolean): Int
Finds index of first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- returns
- the index of the first element of this sequence that satisfies the predicate
p
, or-1
, if none exists.
- the index of the first element of this sequence that satisfies the predicate
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def indexWhere(p: (A) ⇒ Boolean, from: Int): Int
Finds index of the first element satisfying some predicate after or at some start index.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- from
- the start index
- returns
- the index
>= from
of the first element of this sequence that satisfies the predicatep
, or-1
, if none exists.
- the index
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def intersect[B >: A](that: GenSeq[B]): Seq[A]
[use case]
Computes the multiset intersection between this sequence and another sequence.
Note: may not terminate for infinite-sized collections.
- that
- the sequence of elements to intersect with.
- returns
- a new sequence which contains all elements of this sequence which also
appear in
that
. If an element valuex
appears n times inthat
, then the first n occurrences ofx
will be retained in the result, but any following occurrences will be omitted.
- a new sequence which contains all elements of this sequence which also
appear in
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def isDefinedAt(x: Int): Boolean
Tests whether this sequence contains given index.
The implementations of methods apply
and isDefinedAt
turn a Seq[A]
into a
PartialFunction[Int, A]
.
- returns
true
if this sequence contains an element at positionidx
,false
otherwise.
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexOf[B >: A](elem: B): Int
[use case]
Finds index of last occurrence of some value in this sequence.
Note: will not terminate for infinite-sized collections.
- elem
- the element value to search for.
- returns
- the index of the last element of this sequence that is equal (as determined
by
==
) toelem
, or-1
, if none exists.
- the index of the last element of this sequence that is equal (as determined
by
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexOf[B >: A](elem: B, end: Int): Int
[use case]
Finds index of last occurrence of some value in this sequence before or at a given end index.
- elem
- the element value to search for.
- end
- the end index.
- returns
- the index
<= end
of the last element of this sequence that is equal (as determined by==
) toelem
, or-1
, if none exists.
- the index
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexOfSlice[B >: A](that: GenSeq[B]): Int
Finds last index where this sequence contains a given sequence as a slice.
Note: will not terminate for infinite-sized collections.
- that
- the sequence to test
- returns
- the last index such that the elements of this sequence starting a this index
match the elements of sequence
that
, or-1
of no such subsequence exists.
- the last index such that the elements of this sequence starting a this index
match the elements of sequence
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexOfSlice[B >: A](that: GenSeq[B], end: Int): Int
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
- that
- the sequence to test
- end
- the end index
- returns
- the last index
<= end
such that the elements of this sequence starting at this index match the elements of sequencethat
, or-1
of no such subsequence exists.
- the last index
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexWhere(p: (A) ⇒ Boolean): Int
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- returns
- the index of the last element of this sequence that satisfies the predicate
p
, or-1
, if none exists.
- the index of the last element of this sequence that satisfies the predicate
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def lastIndexWhere(p: (A) ⇒ Boolean, end: Int): Int
Finds index of last element satisfying some predicate before or at given end index.
- p
- the predicate used to test elements.
- returns
- the index
<= end
of the last element of this sequence that satisfies the predicatep
, or-1
, if none exists.
- the index
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def lengthCompare(len: Int): Int
Compares the length of this sequence to a test value.
- len
- the test value that gets compared with the length.
- returns
- A value
x
where
- A value
The method as implemented here does not call `length` directly; its running
time is `O(length min len)` instead of `O(length)` . The method should be
overwritten if computing `length` is cheap.
- Definition Classes
- SeqProxyLike → SeqLike
(defined at scala.collection.SeqProxyLike)
def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
A copy of this sequence with an element value appended until a given target length is reached.
- len
- the target length
- elem
- the padding value
- returns
- a new sequence consisting of all elements of this sequence followed by the
minimal number of occurrences of
elem
so that the resulting sequence has a length of at leastlen
.
- a new sequence consisting of all elements of this sequence followed by the
minimal number of occurrences of
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Produces a new sequence where a slice of elements in this sequence is replaced by another sequence.
- from
- the index of the first replaced element
- replaced
- the number of elements to drop in the original sequence
- returns
- a new sequence consisting of all elements of this sequence except that
replaced
elements starting fromfrom
are replaced bypatch
.
- a new sequence consisting of all elements of this sequence except that
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def prefixLength(p: (A) ⇒ Boolean): Int
Returns the length of the longest prefix whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- returns
- the length of the longest prefix of this sequence such that every element of
the segment satisfies the predicate
p
.
- the length of the longest prefix of this sequence such that every element of
the segment satisfies the predicate
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def reverse: Seq[A]
Returns new sequence with elements in reversed order.
Note: will not terminate for infinite-sized collections.
- returns
- A new sequence with all elements of this sequence in reversed order.
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def reverseMap[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Builds a new collection by applying a function to all elements of this sequence and collecting the results in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseMap(f)
is the same as xs.reverse.map(f)
but might be more
efficient.
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new sequence resulting from applying the given function
f
to each element of this sequence and collecting the results in reversed order.
- a new sequence resulting from applying the given function
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def segmentLength(p: (A) ⇒ Boolean, from: Int): Int
Computes length of longest segment whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- from
- the index where the search starts.
- returns
- the length of the longest segment of this sequence starting from index
from
such that every element of the segment satisfies the predicatep
.
- the length of the longest segment of this sequence starting from index
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def sortBy[B](f: (A) ⇒ B)(implicit ord: Ordering[B]): Seq[A]
Sorts this Seq
according to the Ordering which results from transforming an
implicitly given Ordering with a transformation function.
- B
- the target type of the transformation
f
, and the type where the orderingord
is defined.
- the target type of the transformation
- f
- the transformation function mapping elements to some other domain
B
.
- the transformation function mapping elements to some other domain
- ord
- the ordering assumed on domain
B
.
- the ordering assumed on domain
- returns
- a sequence consisting of the elements of this sequence sorted according to
the ordering where
x < y
iford.lt(f(x), f(y))
.
- a sequence consisting of the elements of this sequence sorted according to
the ordering where
- Definition Classes
- SeqProxyLike → SeqLike
- See also
- scala.math.Ordering Note: will not terminate for infinite-sized collections.
Example:
(defined at scala.collection.SeqProxyLike)
def sortWith(lt: (A, A) ⇒ Boolean): Seq[A]
Sorts this sequence according to a comparison function.
Note: will not terminate for infinite-sized collections.
The sort is stable. That is, elements that are equal (as determined by lt
)
appear in the same order in the sorted sequence as in the original.
- lt
- the comparison function which tests whether its first argument precedes its second argument in the desired ordering.
- returns
- a sequence consisting of the elements of this sequence sorted according to
the comparison function
lt
.
- a sequence consisting of the elements of this sequence sorted according to
the comparison function
- Definition Classes
- SeqProxyLike → SeqLike
Example:
(defined at scala.collection.SeqProxyLike)
def sorted[B >: A](implicit ord: Ordering[B]): Seq[A]
Sorts this sequence according to an Ordering.
The sort is stable. That is, elements that are equal (as determined by lt
)
appear in the same order in the sorted sequence as in the original.
- ord
- the ordering to be used to compare elements.
- returns
- a sequence consisting of the elements of this sequence sorted according to
the ordering
ord
.
- a sequence consisting of the elements of this sequence sorted according to
the ordering
- Definition Classes
- SeqProxyLike → SeqLike
- See also
- scala.math.Ordering
(defined at scala.collection.SeqProxyLike)
def startsWith[B](that: GenSeq[B]): Boolean
Tests whether this sequence starts with the given sequence.
- that
- the sequence to test
- returns
true
if this collection hasthat
as a prefix,false
otherwise.
- Definition Classes
- SeqProxyLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def startsWith[B](that: GenSeq[B], offset: Int): Boolean
Tests whether this sequence contains the given sequence at a given index.
Note : If the both the receiver object this
and the argument that
are
infinite sequences this method may not terminate.
- that
- the sequence to test
- offset
- the index where the sequence is searched.
- returns
true
if the sequencethat
is contained in this sequence at indexoffset
, otherwisefalse
.
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Produces a new sequence which contains all elements of this sequence and also
all elements of a given sequence. xs union ys
is equivalent to xs ++ ys
.
Another way to express this is that xs union ys
computes the order-preserving
multi-set union of xs
and ys
. union
is hence a counter-part of diff
and
intersect
which also work on multi-sets.
Note: will not terminate for infinite-sized collections.
- that
- the sequence to add.
- returns
- a new sequence which contains all elements of this sequence followed by all
elements of
that
.
- a new sequence which contains all elements of this sequence followed by all
elements of
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
A copy of this sequence with one single replaced element.
- index
- the position of the replacement
- elem
- the replacing element
- returns
- a copy of this sequence with the element at position
index
replaced byelem
.
- a copy of this sequence with the element at position
- Definition Classes
- SeqProxyLike → SeqLike → GenSeqLike
(defined at scala.collection.SeqProxyLike)
def view(from: Int, until: Int): SeqView[A, Seq[A]]
Creates a non-strict view of a slice of this sequence.
Note: the difference between view
and slice
is that view
produces a view
of the current sequence, whereas slice
produces a new sequence.
Note: view(from, to)
is equivalent to view.slice(from, to)
- from
- the index of the first element of the view
- until
- the index of the element following the view
- returns
- a non-strict view of a slice of this sequence, starting at index
from
and extending up to (but not including) indexuntil
.
- a non-strict view of a slice of this sequence, starting at index
- Definition Classes
- SeqProxyLike → IterableProxyLike → TraversableProxyLike → SeqLike → IterableLike → TraversableLike
(defined at scala.collection.SeqProxyLike)
def view: SeqView[A, Seq[A]]
Creates a non-strict view of this sequence.
- returns
- a non-strict view of this sequence.
- Definition Classes
- SeqProxyLike → IterableProxyLike → TraversableProxyLike → SeqLike → IterableLike → TraversableLike
(defined at scala.collection.SeqProxyLike)
Concrete Value Members From scala.collection.TraversableLike
def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
As with ++
, returns a new collection containing the elements from the left
operand followed by the elements from the right operand.
It differs from ++
in that the right operand determines the type of the
resulting collection rather than the left one. Mnemonic: the COLon is on the
side of the new COLlection type.
Example:
This overload exists because: for the implementation of ++:
we should reuse
that of ++
because many collections override it with more efficient versions.
Since TraversableOnce
has no ++
method, we have to implement that directly,
but Traversable
and down can use the overload.
- B
- the element type of the returned collection.
- That
- the class of the returned collection. Where possible,
That
is the same class as the current collection classRepr
, but this depends on the element typeB
being admissible for that class, which means that an implicit instance of typeCanBuildFrom[Repr, B, That]
is found.
- the class of the returned collection. Where possible,
- that
- the traversable to append.
- bf
- an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and and the new element typeB
.
- an implicit value of class
- returns
- a new collection of type
That
which contains all elements of this traversable collection followed by all elements ofthat
.
- a new collection of type
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
As with ++
, returns a new collection containing the elements from the left
operand followed by the elements from the right operand.
It differs from ++
in that the right operand determines the type of the
resulting collection rather than the left one. Mnemonic: the COLon is on the
side of the new COLlection type.
Example:
- B
- the element type of the returned collection.
- that
- the traversable to append.
- returns
- a new sequence which contains all elements of this sequence followed by all
elements of
that
.
- a new sequence which contains all elements of this sequence followed by all
elements of
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def inits: Iterator[Seq[A]]
Iterates over the inits of this traversable collection. The first value will be
this traversable collection and the final one will be an empty traversable
collection, with the intervening values the results of successive applications
of init
.
- returns
- an iterator over all the inits of this traversable collection
- Definition Classes
- TraversableLike
Example:
(defined at scala.collection.TraversableLike)
def repr: Seq[A]
The collection of type traversable collection underlying this TraversableLike
object. By default this is implemented as the TraversableLike
object itself,
but this can be overridden.
- Definition Classes
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Seq[A], B, That]): That
Computes a prefix scan of the elements of the collection.
Note: The neutral element z
may be applied more than once.
- B
- element type of the resulting collection
- That
- type of the resulting collection
- z
- neutral element for the operator
op
- neutral element for the operator
- op
- the associative operator for the scan
- cbf
- combiner factory which provides a combiner
- returns
- a new traversable collection containing the prefix scan of the elements in this traversable collection
- Definition Classes
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def tails: Iterator[Seq[A]]
Iterates over the tails of this traversable collection. The first value will be
this traversable collection and the final one will be an empty traversable
collection, with the intervening values the results of successive applications
of tail
.
- returns
- an iterator over all the tails of this traversable collection
- Definition Classes
- TraversableLike
Example:
(defined at scala.collection.TraversableLike)
def withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Seq[A]]
Creates a non-strict filter of this traversable collection.
Note: the difference between c filter p
and c withFilter p
is that the
former creates a new collection, whereas the latter only restricts the domain of
subsequent map
, flatMap
, foreach
, and withFilter
operations.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
- the predicate used to test elements.
- returns
- an object of class
WithFilter
, which supportsmap
,flatMap
,foreach
, andwithFilter
operations. All these operations apply to those elements of this traversable collection which satisfy the predicatep
.
- an object of class
- Definition Classes
- TraversableLike → FilterMonadic
(defined at scala.collection.TraversableLike)
Concrete Value Members From scala.collection.TraversableOnce
def aggregate[B](z: ⇒ B)(seqop: (B, A) ⇒ B, combop: (B, B) ⇒ B): B
Aggregates the results of applying an operator to subsequent elements.
This is a more general form of fold
and reduce
. It is similar to
foldLeft
in that it doesn’t require the result to be a supertype of the
element type. In addition, it allows parallel collections to be processed in
chunks, and then combines the intermediate results.
aggregate
splits the traversable or iterator into partitions and processes
each partition by sequentially applying seqop
, starting with z
(like
foldLeft
). Those intermediate results are then combined by using combop
(like fold
). The implementation of this operation may operate on an arbitrary
number of collection partitions (even 1), so combop
may be invoked an
arbitrary number of times (even 0).
As an example, consider summing up the integer values of a list of chars. The
initial value for the sum is 0. First, seqop
transforms each input character
to an Int and adds it to the sum (of the partition). Then, combop
just needs
to sum up the intermediate results of the partitions:
- B
- the type of accumulated results
- z
- the initial value for the accumulated result of the partition - this will
typically be the neutral element for the
seqop
operator (e.g.Nil
for list concatenation or0
for summation) and may be evaluated more than once
- the initial value for the accumulated result of the partition - this will
typically be the neutral element for the
- seqop
- an operator used to accumulate results within a partition
- combop
- an associative operator used to combine results from different partitions
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def collectFirst[B](pf: PartialFunction[A, B]): Option[B]
Finds the first element of the traversable or iterator for which the given partial function is defined, and applies the partial function to it.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- pf
- the partial function
- returns
- an option value containing pf applied to the first value for which it is
defined, or
None
if none exists.
- an option value containing pf applied to the first value for which it is
defined, or
- Definition Classes
- TraversableOnce
Example:
(defined at scala.collection.TraversableOnce)
def fold[A1 >: A](z: A1)(op: (A1, A1) ⇒ A1): A1
Folds the elements of this traversable or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
- A1
- a type parameter for the binary operator, a supertype of
A
.
- a type parameter for the binary operator, a supertype of
- z
- a neutral element for the fold operation; may be added to the result an
arbitrary number of times, and must not change the result (e.g.,
Nil
for list concatenation, 0 for addition, or 1 for multiplication).
- a neutral element for the fold operation; may be added to the result an
arbitrary number of times, and must not change the result (e.g.,
- op
- a binary operator that must be associative.
- returns
- the result of applying the fold operator
op
between all the elements andz
, orz
if this traversable or iterator is empty.
- the result of applying the fold operator
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
[use case]
Finds the first element which yields the largest value measured by function f.
- B
- The result type of the function f.
- f
- The measuring function.
- returns
- the first element of this sequence with the largest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
[use case]
Finds the first element which yields the smallest value measured by function f.
- B
- The result type of the function f.
- f
- The measuring function.
- returns
- the first element of this sequence with the smallest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def reduceOption[A1 >: A](op: (A1, A1) ⇒ A1): Option[A1]
Reduces the elements of this traversable or iterator, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- A1
- A type parameter for the binary operator, a supertype of
A
.
- A type parameter for the binary operator, a supertype of
- op
- A binary operator that must be associative.
- returns
- An option value containing result of applying reduce operator
op
between all the elements if the collection is nonempty, andNone
otherwise.
- An option value containing result of applying reduce operator
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1
Reduces the elements of this traversable or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- A1
- A type parameter for the binary operator, a supertype of
A
.
- A type parameter for the binary operator, a supertype of
- op
- A binary operator that must be associative.
- returns
- The result of applying reduce operator
op
between all the elements if the traversable or iterator is nonempty.
- The result of applying reduce operator
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this traversable or iterator is empty.
(defined at scala.collection.TraversableOnce)
Abstract Value Members From scala.collection.TraversableProxyLike
abstract def self: Seq[A]
- Definition Classes
- TraversableProxyLike → Proxy
(defined at scala.collection.TraversableProxyLike)
Concrete Value Members From scala.collection.TraversableProxyLike
def ++[B >: A, That](xs: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the sequence is the most specific superclass encompassing the element types of the two operands.
Example:
- B
- the element type of the returned collection.
- that
- the traversable to append.
- returns
- a new sequence which contains all elements of this sequence followed by all
elements of
that
.
- a new sequence which contains all elements of this sequence followed by all
elements of
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def /:[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable collection, going left to right.
Note: /:
is alternate syntax for foldLeft
; z /: xs
is the same as
xs foldLeft z
.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- z
- the start value.
- op
- the binary operator.
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going left to right with the start valuez
on the left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def :\[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable collection and a start value, going right to left.
Note: :\
is alternate syntax for foldRight
; xs :\ z
is the same as
xs foldRight z
.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
- B
- the result type of the binary operator.
- z
- the start value
- op
- the binary operator
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going right to left with the start valuez
on the right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def addString(b: mutable.StringBuilder): mutable.StringBuilder
Appends all elements of this traversable collection to a string builder. The
written text consists of the string representations (w.r.t. the method
toString
) of all elements of this traversable collection without any
separator string.
Example:
- b
- the string builder to which elements are appended.
- returns
- the string builder
b
to which elements were appended.
- the string builder
- Definition Classes
- TraversableProxyLike → TraversableOnce
(defined at scala.collection.TraversableProxyLike)
def addString(b: mutable.StringBuilder, sep: String): mutable.StringBuilder
Appends all elements of this traversable collection to a string builder using a
separator string. The written text consists of the string representations
(w.r.t. the method toString
) of all elements of this traversable collection,
separated by the string sep
.
Example:
- b
- the string builder to which elements are appended.
- sep
- the separator string.
- returns
- the string builder
b
to which elements were appended.
- the string builder
- Definition Classes
- TraversableProxyLike → TraversableOnce
(defined at scala.collection.TraversableProxyLike)
def addString(b: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder
Appends all elements of this traversable collection to a string builder using
start, end, and separator strings. The written text begins with the string
start
and ends with the string end
. Inside, the string representations
(w.r.t. the method toString
) of all elements of this traversable collection
are separated by the string sep
.
Example:
- b
- the string builder to which elements are appended.
- start
- the starting string.
- sep
- the separator string.
- end
- the ending string.
- returns
- the string builder
b
to which elements were appended.
- the string builder
- Definition Classes
- TraversableProxyLike → TraversableOnce
(defined at scala.collection.TraversableProxyLike)
def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Builds a new collection by applying a partial function to all elements of this sequence on which the function is defined.
- B
- the element type of the returned collection.
- pf
- the partial function which filters and maps the sequence.
- returns
- a new sequence resulting from applying the given partial function
pf
to each element on which it is defined and collecting the results. The order of the elements is preserved.
- a new sequence resulting from applying the given partial function
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def copyToArray[B >: A](xs: Array[B]): Unit
[use case]
Copies the elements of this sequence to an array. Fills the given array xs
with values of this sequence. Copying will stop once either the end of the
current sequence is reached, or the end of the target array is reached.
Note: will not terminate for infinite-sized collections.
- xs
- the array to fill.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def copyToArray[B >: A](xs: Array[B], start: Int): Unit
[use case]
Copies the elements of this sequence to an array. Fills the given array xs
with values of this sequence, beginning at index start
. Copying will stop
once either the end of the current sequence is reached, or the end of the target
array is reached.
Note: will not terminate for infinite-sized collections.
- xs
- the array to fill.
- start
- the starting index.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit
[use case]
Copies the elements of this sequence to an array. Fills the given array xs
with at most len
elements of this sequence, starting at position start
.
Copying will stop once either the end of the current sequence is reached, or the
end of the target array is reached, or len
elements have been copied.
Note: will not terminate for infinite-sized collections.
- xs
- the array to fill.
- start
- the starting index.
- len
- the maximal number of elements to copy.
- Definition Classes
- TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Copies all elements of this traversable collection to a buffer.
Note: will not terminate for infinite-sized collections.
- dest
- The buffer to which elements are copied.
- Definition Classes
- TraversableProxyLike → TraversableOnce
(defined at scala.collection.TraversableProxyLike)
def count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the traversable collection which satisfy a predicate.
- p
- the predicate used to test elements.
- returns
- the number of elements satisfying the predicate
p
.
- the number of elements satisfying the predicate
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def drop(n: Int): Seq[A]
Selects all elements except first n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
- the number of elements to drop from this traversable collection.
- returns
- a traversable collection consisting of all elements of this traversable
collection except the first
n
ones, or else the empty traversable collection, if this traversable collection has less thann
elements.
- a traversable collection consisting of all elements of this traversable
collection except the first
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def dropWhile(p: (A) ⇒ Boolean): Seq[A]
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- the longest suffix of this traversable collection whose first element does
not satisfy the predicate
p
.
- the longest suffix of this traversable collection whose first element does
not satisfy the predicate
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this traversable collection.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- returns
false
if this traversable collection is empty, otherwisetrue
if the given predicatep
holds for some of the elements of this traversable collection, otherwisefalse
- Definition Classes
- TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def filter(p: (A) ⇒ Boolean): Seq[A]
Selects all elements of this traversable collection which satisfy a predicate.
- p
- the predicate used to test elements.
- returns
- a new traversable collection consisting of all elements of this traversable
collection that satisfy the given predicate
p
. The order of the elements is preserved.
- a new traversable collection consisting of all elements of this traversable
collection that satisfy the given predicate
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def filterNot(p: (A) ⇒ Boolean): Seq[A]
Selects all elements of this traversable collection which do not satisfy a predicate.
- p
- the predicate used to test elements.
- returns
- a new traversable collection consisting of all elements of this traversable
collection that do not satisfy the given predicate
p
. The order of the elements is preserved.
- a new traversable collection consisting of all elements of this traversable
collection that do not satisfy the given predicate
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the traversable collection satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
- the predicate used to test elements.
- returns
- an option value containing the first element in the traversable collection
that satisfies
p
, orNone
if none exists.
- an option value containing the first element in the traversable collection
that satisfies
- Definition Classes
- TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Builds a new collection by applying a function to all elements of this sequence and using the elements of the resulting collections.
For example:
The type of the resulting collection is guided by the static type of sequence. This might cause unexpected results sometimes. For example:
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new sequence resulting from applying the given collection-valued function
f
to each element of this sequence and concatenating the results.
- a new sequence resulting from applying the given collection-valued function
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike → FilterMonadic
(defined at scala.collection.TraversableProxyLike)
def foldLeft[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable collection, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- z
- the start value.
- op
- the binary operator.
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going left to right with the start valuez
on the left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection. Returns
`z` if this traversable collection is empty.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def foldRight[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable collection and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- z
- the start value.
- op
- the binary operator.
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going right to left with the start valuez
on the right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection. Returns
`z` if this traversable collection is empty.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this traversable collection.
Note: may not terminate for infinite-sized collections.
- p
- the predicate used to test elements.
- returns
true
if this traversable collection is empty or the given predicatep
holds for all elements of this traversable collection, otherwisefalse
.
- Definition Classes
- TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def foreach[U](f: (A) ⇒ U): Unit
[use case]
Applies a function f
to all elements of this sequence.
Note: this method underlies the implementation of most other bulk operations. It’s important to implement this method in an efficient way.
- f
- the function that is applied for its side-effect to every element. The
result of function
f
is discarded.
- the function that is applied for its side-effect to every element. The
result of function
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike → TraversableOnce → GenTraversableOnce → FilterMonadic
(defined at scala.collection.TraversableProxyLike)
def groupBy[K](f: (A) ⇒ K): immutable.Map[K, Seq[A]]
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new traversable collection.
- K
- the type of keys returned by the discriminator function.
- f
- the discriminator function.
- returns
- A map from keys to traversable collections such that the following invariant holds:
That is, every key `k` is bound to a traversable collection of those
elements `x` for which `f(x)` equals `k` .
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def init: Seq[A]
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- a traversable collection consisting of all elements of this traversable collection except the last one.
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
- Exceptions thrown
- UnsupportedOperationException if the traversable collection is empty.
(defined at scala.collection.TraversableProxyLike)
def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
[use case]
Builds a new collection by applying a function to all elements of this sequence.
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new sequence resulting from applying the given function
f
to each element of this sequence and collecting the results.
- a new sequence resulting from applying the given function
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike → FilterMonadic
(defined at scala.collection.TraversableProxyLike)
def mkString(sep: String): String
Displays all elements of this traversable collection in a string using a separator string.
- sep
- the separator string.
- returns
- a string representation of this traversable collection. In the resulting
string the string representations (w.r.t. the method
toString
) of all elements of this traversable collection are separated by the stringsep
.
- a string representation of this traversable collection. In the resulting
string the string representations (w.r.t. the method
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
Example:
(defined at scala.collection.TraversableProxyLike)
def mkString(start: String, sep: String, end: String): String
Displays all elements of this traversable collection in a string using start, end, and separator strings.
- start
- the starting string.
- sep
- the separator string.
- end
- the ending string.
- returns
- a string representation of this traversable collection. The resulting string
begins with the string
start
and ends with the stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this traversable collection are separated by the stringsep
.
- a string representation of this traversable collection. The resulting string
begins with the string
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
Example:
(defined at scala.collection.TraversableProxyLike)
def partition(p: (A) ⇒ Boolean): (Seq[A], Seq[A])
Partitions this traversable collection in two traversable collections according to a predicate.
- p
- the predicate on which to partition.
- returns
- a pair of traversable collections: the first traversable collection consists
of all elements that satisfy the predicate
p
and the second traversable collection consists of all elements that don’t. The relative order of the elements in the resulting traversable collections is the same as in the original traversable collection.
- a pair of traversable collections: the first traversable collection consists
of all elements that satisfy the predicate
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def reduceLeftOption[B >: A](op: (B, A) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable collection, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- op
- the binary operator.
- returns
- an option value containing the result of
reduceLeft(op)
if this traversable collection is nonempty,None
otherwise.
- an option value containing the result of
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def reduceLeft[B >: A](op: (B, A) ⇒ B): B
Applies a binary operator to all elements of this traversable collection, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- op
- the binary operator.
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going left to right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this traversable collection is empty.
(defined at scala.collection.TraversableProxyLike)
def reduceRightOption[B >: A](op: (A, B) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable collection, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- op
- the binary operator.
- returns
- an option value containing the result of
reduceRight(op)
if this traversable collection is nonempty,None
otherwise.
- an option value containing the result of
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable collection, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
- B
- the result type of the binary operator.
- op
- the binary operator.
- returns
- the result of inserting
op
between consecutive elements of this traversable collection, going right to left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this traversable collection is empty.
(defined at scala.collection.TraversableProxyLike)
def scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
Produces a collection containing cumulative results of applying the operator going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- B
- the type of the elements in the resulting collection
- That
- the actual type of the resulting collection
- z
- the initial value
- op
- the binary operator applied to the intermediate result and the element
- bf
- an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and and the new element typeB
.
- an implicit value of class
- returns
- collection with intermediate results
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Seq[A], B, That]): That
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Example:
- B
- the type of the elements in the resulting collection
- That
- the actual type of the resulting collection
- z
- the initial value
- op
- the binary operator applied to the intermediate result and the element
- bf
- an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and and the new element typeB
.
- an implicit value of class
- returns
- collection with intermediate results
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def slice(from: Int, until: Int): Seq[A]
Selects an interval of elements. The returned collection is made up of all
elements x
which satisfy the invariant:
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- a traversable collection containing the elements greater than or equal to
index
from
extending up to (but not including) indexuntil
of this traversable collection.
- a traversable collection containing the elements greater than or equal to
index
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def span(p: (A) ⇒ Boolean): (Seq[A], Seq[A])
Splits this traversable collection into a prefix/suffix pair according to a predicate.
Note: c span p
is equivalent to (but possibly more efficient than)
(c takeWhile p, c dropWhile p)
, provided the evaluation of the predicate
p
does not cause any side-effects.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- a pair consisting of the longest prefix of this traversable collection whose
elements all satisfy
p
, and the rest of this traversable collection.
- a pair consisting of the longest prefix of this traversable collection whose
elements all satisfy
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def splitAt(n: Int): (Seq[A], Seq[A])
Splits this traversable collection into two at a given position. Note:
c splitAt n
is equivalent to (but possibly more efficient than)
(c take n, c drop n)
.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
- the position at which to split.
- returns
- a pair of traversable collections consisting of the first
n
elements of this traversable collection, and the other elements.
- a pair of traversable collections consisting of the first
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def tail: Seq[A]
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- a traversable collection consisting of all elements of this traversable collection except the first one.
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
- Exceptions thrown
UnsupportedOperationException
if the traversable collection is empty.
(defined at scala.collection.TraversableProxyLike)
def take(n: Int): Seq[A]
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
- the number of elements to take from this traversable collection.
- returns
- a traversable collection consisting only of the first
n
elements of this traversable collection, or else the whole traversable collection, if it has less thann
elements.
- a traversable collection consisting only of the first
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def takeWhile(p: (A) ⇒ Boolean): Seq[A]
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- the longest prefix of this traversable collection whose elements all satisfy
the predicate
p
.
- the longest prefix of this traversable collection whose elements all satisfy
the predicate
- Definition Classes
- TraversableProxyLike → TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableProxyLike)
def toBuffer[B >: A]: Buffer[B]
Uses the contents of this traversable collection to create a new mutable buffer.
Note: will not terminate for infinite-sized collections.
- returns
- a buffer containing all elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def toIndexedSeq: immutable.IndexedSeq[A]
Converts this traversable collection to an indexed sequence.
Note: will not terminate for infinite-sized collections.
- returns
- an indexed sequence containing all elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def toMap[T, U](implicit ev: <:<[A, (T, U)]): immutable.Map[T, U]
[use case]
Converts this sequence to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.
Note: will not terminate for infinite-sized collections.
- returns
- a map of type
immutable.Map[T, U]
containing all key/value pairs of type(T, U)
of this sequence.
- a map of type
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
def toSet[B >: A]: immutable.Set[B]
Converts this traversable collection to a set.
Note: will not terminate for infinite-sized collections.
- returns
- a set containing all elements of this traversable collection.
- Definition Classes
- TraversableProxyLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableProxyLike)
Concrete Value Members From scala.collection.generic.GenericTraversableTemplate ——————————————————————————–
def genericBuilder[B]: Builder[B, Seq[B]]
The generic builder that builds instances of Traversable at arbitrary element types.
- Definition Classes
- GenericTraversableTemplate
(defined at scala.collection.generic.GenericTraversableTemplate)
def newBuilder: Builder[A, Seq[A]]
The builder that builds instances of type Traversable[A]
- Attributes
- protected[this]
- Definition Classes
- GenericTraversableTemplate → HasNewBuilder
(defined at scala.collection.generic.GenericTraversableTemplate)
def transpose[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Seq[Seq[B]]
Transposes this collection of traversable collections into a collection of collections.
The resulting collection’s type will be guided by the static type of collection. For example:
- B
- the type of the elements of each traversable collection.
- asTraversable
- an implicit conversion which asserts that the element type of this
collection is a
Traversable
.
- an implicit conversion which asserts that the element type of this
collection is a
- returns
- a two-dimensional collection of collections which has as n th row the n th column of this collection.
- Definition Classes
- GenericTraversableTemplate
- Annotations
- @migration
- Migration
- (Changed in version 2.9.0)
transpose
throws anIllegalArgumentException
if collections are not uniformly sized.
- (Changed in version 2.9.0)
- Exceptions thrown
- IllegalArgumentException if all collections in this collection are not of the same size.
(defined at scala.collection.generic.GenericTraversableTemplate)
def unzip3[A1, A2, A3](implicit asTriple: (A) ⇒ (A1, A2, A3)): (Seq[A1], Seq[A2], Seq[A3])
Converts this collection of triples into three collections of the first, second, and third element of each triple.
- A1
- the type of the first member of the element triples
- A2
- the type of the second member of the element triples
- A3
- the type of the third member of the element triples
- asTriple
- an implicit conversion which asserts that the element type of this collection is a triple.
- returns
- a triple of collections, containing the first, second, respectively third member of each element triple of this collection.
- Definition Classes
- GenericTraversableTemplate
(defined at scala.collection.generic.GenericTraversableTemplate)
def unzip[A1, A2](implicit asPair: (A) ⇒ (A1, A2)): (Seq[A1], Seq[A2])
Converts this collection of pairs into two collections of the first and second half of each pair.
- A1
- the type of the first half of the element pairs
- A2
- the type of the second half of the element pairs
- asPair
- an implicit conversion which asserts that the element type of this collection is a pair.
- returns
- a pair of collections, containing the first, respectively second half of each element pair of this collection.
- Definition Classes
- GenericTraversableTemplate
(defined at scala.collection.generic.GenericTraversableTemplate)
Concrete Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–
def toParArray: ParArray[T]
- Implicit information
- This member is added by an implicit conversion from SeqProxy [A] to CollectionsHaveToParArray [SeqProxy [A], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (SeqProxy [A]) ⇒ GenTraversableOnce [T] is in scope.
- Definition Classes
- CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)
Full Source:
Interested in Scala?
I send out weekly, personalized emails with articles and conference talks.
Subscribe now.