Scala Library: scala.collection.AbstractTraversable
scala.collection.AbstractTraversable
Explicit instantiation of the Traversable
trait to reduce class file size in
subclasses.
Type Members
type Self = Traversable[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
Instance Constructors From scala.collection.AbstractTraversable
new AbstractTraversable()
(defined at scala.collection.AbstractTraversable)
Value Members From scala.collection.Parallelizable
def par: ParIterable[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)
Value Members From scala.collection.Traversable
def companion: GenericCompanion[Traversable]
The factory companion object that builds instances of class Traversable. (or its
Iterable
superclass where class Traversable is not a Seq
.)
- Definition Classes
- Traversable → GenTraversable → GenericTraversableTemplate
(defined at scala.collection.Traversable)
Value Members From scala.collection.TraversableLike
def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Traversable[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[Traversable[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 collection which contains all elements of this collection followed by
all elements of
that
.
- a new collection which contains all elements of this collection followed by
all elements of
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
[use case]
Returns a new collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the collection 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 collection which contains all elements of this collection followed by
all elements of
that
.
- a new collection which contains all elements of this collection followed by
all elements of
- Definition Classes
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
[use case]
Builds a new collection by applying a partial function to all elements of this collection on which the function is defined.
- B
- the element type of the returned collection.
- pf
- the partial function which filters and maps the collection.
- returns
- a new collection 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 collection resulting from applying the given partial function
- Definition Classes
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit
[use case]
Copies the elements of this collection to an array. Fills the given array xs
with at most len
elements of this collection, starting at position start
.
Copying will stop once either the end of the current collection 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
- TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableLike)
def drop(n: Int): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def dropWhile(p: (A) ⇒ Boolean): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
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
- TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableLike)
def filter(p: (A) ⇒ Boolean): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def filterNot(p: (A) ⇒ Boolean): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
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
- TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableLike)
def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
[use case]
Builds a new collection by applying a function to all elements of this collection and using the elements of the resulting collections.
For example:
The type of the resulting collection is guided by the static type of collection. 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 collection resulting from applying the given collection-valued
function
f
to each element of this collection and concatenating the results.
- a new collection resulting from applying the given collection-valued
function
- Definition Classes
- TraversableLike → GenTraversableLike → FilterMonadic
(defined at scala.collection.TraversableLike)
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
- TraversableLike → TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableLike)
def groupBy[K](f: (A) ⇒ K): immutable.Map[K, Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def init: Traversable[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
- TraversableLike → GenTraversableLike
- Exceptions thrown
- UnsupportedOperationException if the traversable collection is empty.
(defined at scala.collection.TraversableLike)
def inits: Iterator[Traversable[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 map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
[use case]
Builds a new collection by applying a function to all elements of this collection.
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new collection resulting from applying the given function
f
to each element of this collection and collecting the results.
- a new collection resulting from applying the given function
- Definition Classes
- TraversableLike → GenTraversableLike → FilterMonadic
(defined at scala.collection.TraversableLike)
def parCombiner: Combiner[A, ParIterable[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
- TraversableLike → Parallelizable
(defined at scala.collection.TraversableLike)
def partition(p: (A) ⇒ Boolean): (Traversable[A], Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def repr: Traversable[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 scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Traversable[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
- TraversableLike → GenTraversableLike
- Annotations
- @migration
- Migration
- (Changed in version 2.9.0) The behavior of
scanRight
has changed. The previous behavior can be reproduced with scanRight.reverse.
- (Changed in version 2.9.0) The behavior of
(defined at scala.collection.TraversableLike)
def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Traversable[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 slice(from: Int, until: Int): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def span(p: (A) ⇒ Boolean): (Traversable[A], Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def splitAt(n: Int): (Traversable[A], Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def tail: Traversable[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
- TraversableLike → GenTraversableLike
- Exceptions thrown
UnsupportedOperationException
if the traversable collection is empty.
(defined at scala.collection.TraversableLike)
def tails: Iterator[Traversable[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 take(n: Int): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def takeWhile(p: (A) ⇒ Boolean): Traversable[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
- TraversableLike → GenTraversableLike
(defined at scala.collection.TraversableLike)
def toCollection(repr: Traversable[A]): Traversable[A]
A conversion from collections of type Repr
to Traversable
objects. By
default this is implemented as just a cast, but this can be overridden.
- Attributes
- protected[this]
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def view(from: Int, until: Int): TraversableView[A, Traversable[A]]
Creates a non-strict view of a slice of this traversable collection.
Note: the difference between view
and slice
is that view
produces a view
of the current traversable collection, whereas slice
produces a new
traversable collection.
Note: view(from, to)
is equivalent to view.slice(from, to)
Note: might return different results for different runs, unless the underlying collection type is ordered.
- 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 traversable collection, starting at
index
from
and extending up to (but not including) indexuntil
.
- a non-strict view of a slice of this traversable collection, starting at
index
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def view: TraversableView[A, Traversable[A]]
Creates a non-strict view of this traversable collection.
- returns
- a non-strict view of this traversable collection.
- Definition Classes
- TraversableLike
(defined at scala.collection.TraversableLike)
def withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Traversable[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)
Value Members From scala.collection.TraversableOnce
def /:[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable or iterator, 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 or iterator, going left to right with the start valuez
on the left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def :\[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator 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 or iterator, going right to left with the start valuez
on the right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def addString(b: StringBuilder): StringBuilder
Appends all elements of this traversable or iterator to a string builder. The
written text consists of the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator 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
- TraversableOnce
(defined at scala.collection.TraversableOnce)
def addString(b: StringBuilder, sep: String): StringBuilder
Appends all elements of this traversable or iterator 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 or iterator,
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
- TraversableOnce
(defined at scala.collection.TraversableOnce)
def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder
Appends all elements of this traversable or iterator 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 or iterator
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
- TraversableOnce
(defined at 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 copyToArray[B >: A](xs: Array[B]): Unit
[use case]
Copies the elements of this collection to an array. Fills the given array xs
with values of this collection. Copying will stop once either the end of the
current collection 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
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def copyToArray[B >: A](xs: Array[B], start: Int): Unit
[use case]
Copies the elements of this collection to an array. Fills the given array xs
with values of this collection, beginning at index start
. Copying will stop
once either the end of the current collection 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
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Copies all elements of this traversable or iterator to a buffer.
Note: will not terminate for infinite-sized collections.
- dest
- The buffer to which elements are copied.
- Definition Classes
- TraversableOnce
(defined at scala.collection.TraversableOnce)
def count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the traversable or iterator 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
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def foldLeft[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this traversable or iterator, 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 or iterator, going left to right with the start valuez
on the left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
Returns `z` if this traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def foldRight[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator 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 or iterator, going right to left with the start valuez
on the right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
Returns `z` if this traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(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 collection 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 collection with the smallest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def mkString(sep: String): String
Displays all elements of this traversable or iterator in a string using a separator string.
- sep
- the separator string.
- returns
- a string representation of this traversable or iterator. In the resulting
string the string representations (w.r.t. the method
toString
) of all elements of this traversable or iterator are separated by the stringsep
.
- a string representation of this traversable or iterator. In the resulting
string the string representations (w.r.t. the method
- Definition Classes
- TraversableOnce → GenTraversableOnce
Example:
(defined at scala.collection.TraversableOnce)
def mkString(start: String, sep: String, end: String): String
Displays all elements of this traversable or iterator 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 or iterator. 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 or iterator are separated by the stringsep
.
- a string representation of this traversable or iterator. The resulting
string begins with the string
- Definition Classes
- TraversableOnce → GenTraversableOnce
Example:
(defined at scala.collection.TraversableOnce)
def reduceLeftOption[B >: A](op: (B, A) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable or iterator, 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 or iterator is nonempty,None
otherwise.
- an option value containing the result of
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def reduceLeft[B >: A](op: (B, A) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator, 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 or iterator, going left to right:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this traversable or iterator is empty.
(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 reduceRightOption[B >: A](op: (A, B) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this traversable or iterator, 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 or iterator is nonempty,None
otherwise.
- an option value containing the result of
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator, 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 or iterator, going right to left:
- the result of inserting
where `x1, ..., xn` are the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this traversable or iterator is empty.
(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)
def toBuffer[B >: A]: Buffer[B]
Uses the contents of this traversable or iterator to create a new mutable buffer.
Note: will not terminate for infinite-sized collections.
- returns
- a buffer containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def toIndexedSeq: immutable.IndexedSeq[A]
Converts this traversable or iterator to an indexed sequence.
Note: will not terminate for infinite-sized collections.
- returns
- an indexed sequence containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def toMap[T, U](implicit ev: <:<[A, (T, U)]): immutable.Map[T, U]
[use case]
Converts this collection 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 collection.
- a map of type
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
def toSet[B >: A]: immutable.Set[B]
Converts this traversable or iterator to a set.
Note: will not terminate for infinite-sized collections.
- returns
- a set containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
(defined at scala.collection.TraversableOnce)
Value Members From scala.collection.generic.GenericTraversableTemplate
abstract def foreach[U](f: (A) ⇒ U): Unit
[use case]
- 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
- GenericTraversableTemplate
(defined at scala.collection.generic.GenericTraversableTemplate)
def genericBuilder[B]: Builder[B, Traversable[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, Traversable[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]): Traversable[Traversable[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)): (Traversable[A1], Traversable[A2], Traversable[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)): (Traversable[A1], Traversable[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)
Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–
def toParArray: ParArray[T]
- Implicit information
- This member is added by an implicit conversion from AbstractTraversable [A] to CollectionsHaveToParArray [AbstractTraversable [A], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type ( AbstractTraversable [A]) ⇒ GenTraversableOnce [T] is in scope.
- Definition Classes
- CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)
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