trait GenTraversableLike[+A, +Repr] extends GenTraversableOnce[A] with Parallelizable[A, ParIterable[A]]
A template trait for all traversable collections upon which operations may be implemented in parallel.
- Source
- GenTraversableLike.scala
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- GenTraversableLike
- Parallelizable
- GenTraversableOnce
- Any
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- by ArrowAssoc
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Abstract Value Members
-
abstract
def
++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That
Returns a new general collection containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new general collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the general collection is the most specific superclass encompassing the element types of the two operands.
- 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.- that
the traversable to append.
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
a new collection of type
That
which contains all elements of this general collection followed by all elements ofthat
.
-
abstract
def
aggregate[B](z: ⇒ B)(seqop: (B, A) ⇒ B, combop: (B, B) ⇒ B): B
Aggregates the results of applying an operator to subsequent elements.
Aggregates the results of applying an operator to subsequent elements.
This is a more general form of
fold
andreduce
. It is similar tofoldLeft
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 collection or iterator into partitions and processes each partition by sequentially applyingseqop
, starting withz
(likefoldLeft
). Those intermediate results are then combined by usingcombop
(likefold
). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), socombop
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:List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })
- 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- seqop
an operator used to accumulate results within a partition
- combop
an associative operator used to combine results from different partitions
- Definition Classes
- GenTraversableOnce
-
abstract
def
count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the collection or iterator which satisfy a predicate.
Counts the number of elements in the collection or iterator which satisfy a predicate.
- p
the predicate used to test elements.
- returns
the number of elements satisfying the predicate
p
.
- Definition Classes
- GenTraversableOnce
-
abstract
def
drop(n: Int): Repr
Selects all elements except first n ones.
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 general collection.
- returns
a general collection consisting of all elements of this general collection except the first
n
ones, or else the empty general collection, if this general collection has less thann
elements. Ifn
is negative, don't drop any elements.
-
abstract
def
dropWhile(pred: (A) ⇒ Boolean): Repr
Drops longest prefix of elements that satisfy a predicate.
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- pred
The predicate used to test elements.
- returns
the longest suffix of this general collection whose first element does not satisfy the predicate
p
.
-
abstract
def
exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this collection or iterator.
Tests whether a predicate holds for at least one element of this collection or iterator.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if the given predicatep
is satisfied by at least one element of this collection or iterator, otherwisefalse
- Definition Classes
- GenTraversableOnce
-
abstract
def
filter(pred: (A) ⇒ Boolean): Repr
Selects all elements of this general collection which satisfy a predicate.
Selects all elements of this general collection which satisfy a predicate.
- pred
the predicate used to test elements.
- returns
a new general collection consisting of all elements of this general collection that satisfy the given predicate
p
. Their order may not be preserved.
-
abstract
def
filterNot(pred: (A) ⇒ Boolean): Repr
Selects all elements of this general collection which do not satisfy a predicate.
Selects all elements of this general collection which do not satisfy a predicate.
- pred
the predicate used to test elements.
- returns
a new general collection consisting of all elements of this general collection that do not satisfy the given predicate
p
. Their order may not be preserved.
-
abstract
def
find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the collection or iterator satisfying a predicate, if any.
Finds the first element of the collection or iterator 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 collection or iterator that satisfies
p
, orNone
if none exists.
- Definition Classes
- GenTraversableOnce
-
abstract
def
fold[A1 >: A](z: A1)(op: (A1, A1) ⇒ A1): A1
Folds the elements of this collection or iterator using the specified associative binary operator.
Folds the elements of this collection 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
.- 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).- 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 collection or iterator is empty.
- Definition Classes
- GenTraversableOnce
-
abstract
def
foldLeft[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.
Applies a binary operator to a start value and all elements of this collection 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 collection or iterator, going left to right with the start valuez
on the left:op(...op(z, x_1), x_2, ..., x_n)
where
x1, ..., xn
are the elements of this collection or iterator. Returnsz
if this collection or iterator is empty.
- Definition Classes
- GenTraversableOnce
-
abstract
def
foldRight[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.
Applies a binary operator to all elements of this collection 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 collection or iterator, going right to left with the start valuez
on the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xn
are the elements of this collection or iterator. Returnsz
if this collection or iterator is empty.
- Definition Classes
- GenTraversableOnce
-
abstract
def
forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this collection or iterator.
Tests whether a predicate holds for all elements of this collection or iterator.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if this collection or iterator is empty or the given predicatep
holds for all elements of this collection or iterator, otherwisefalse
.
- Definition Classes
- GenTraversableOnce
-
abstract
def
getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
- Definition Classes
- Any
-
abstract
def
groupBy[K](f: (A) ⇒ K): GenMap[K, Repr]
Partitions this general collection into a map of general collections according to some discriminator function.
Partitions this general collection into a map of general 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 general collection.
- K
the type of keys returned by the discriminator function.
- f
the discriminator function.
- returns
A map from keys to general collections such that the following invariant holds:
(xs groupBy f)(k) = xs filter (x => f(x) == k)
That is, every key
k
is bound to a general collection of those elementsx
for whichf(x)
equalsk
.
-
abstract
def
hasDefiniteSize: Boolean
Tests whether this collection or iterator is known to have a finite size.
Tests whether this collection or iterator is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as
Stream
, the predicate returnstrue
if all elements have been computed. It returnsfalse
if the stream is not yet evaluated to the end. Non-empty Iterators usually returnfalse
even if they were created from a collection with a known finite size.Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that
hasDefiniteSize
returnstrue
. However, checkinghasDefiniteSize
can provide an assurance that size is well-defined and non-termination is not a concern.- returns
true
if this collection is known to have finite size,false
otherwise.
- Definition Classes
- GenTraversableOnce
-
abstract
def
head: A
Selects the first element of this general collection.
Selects the first element of this general collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the first element of this general collection.
- Exceptions thrown
NoSuchElementException
if the general collection is empty.
-
abstract
def
headOption: Option[A]
Optionally selects the first element.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the first element of this general collection if it is nonempty,
None
if it is empty.
-
abstract
def
init: Repr
Selects all elements except the last.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a general collection consisting of all elements of this general collection except the last one.
- Exceptions thrown
UnsupportedOperationException
if the general collection is empty.
-
abstract
def
isEmpty: Boolean
Tests whether the collection or iterator is empty.
Tests whether the collection or iterator is empty.
Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when
isEmpty
is called.- returns
true
if the collection or iterator contains no elements,false
otherwise.
- Definition Classes
- GenTraversableOnce
-
abstract
def
isTraversableAgain: Boolean
Tests whether this general collection can be repeatedly traversed.
Tests whether this general collection can be repeatedly traversed.
- returns
true
- Definition Classes
- GenTraversableLike → GenTraversableOnce
-
abstract
def
last: A
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
The last element of this general collection.
- Exceptions thrown
NoSuchElementException
If the general collection is empty.
-
abstract
def
lastOption: Option[A]
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the last element of this general collection$ if it is nonempty,
None
if it is empty.
-
abstract
def
mkString: String
Displays all elements of this collection or iterator in a string.
Displays all elements of this collection or iterator in a string.
- returns
a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection or iterator follow each other without any separator string.
- Definition Classes
- GenTraversableOnce
-
abstract
def
mkString(sep: String): String
Displays all elements of this collection or iterator in a string using a separator string.
Displays all elements of this collection or iterator in a string using a separator string.
- sep
the separator string.
- returns
a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection or iterator are separated by the stringsep
.
- Definition Classes
- GenTraversableOnce
List(1, 2, 3).mkString("|") = "1|2|3"
Example: -
abstract
def
mkString(start: String, sep: String, end: String): String
Displays all elements of this collection or iterator in a string using start, end, and separator strings.
Displays all elements of this collection 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 collection 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 collection or iterator are separated by the stringsep
.
- Definition Classes
- GenTraversableOnce
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Example: -
abstract
def
nonEmpty: Boolean
Tests whether the collection or iterator is not empty.
Tests whether the collection or iterator is not empty.
- returns
true
if the collection or iterator contains at least one element,false
otherwise.
- Definition Classes
- GenTraversableOnce
-
abstract
def
parCombiner: Combiner[A, ParIterable[A]]
The default
par
implementation uses the combiner provided by this method to create a new parallel collection.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
- Attributes
- protected[this]
- Definition Classes
- Parallelizable
-
abstract
def
partition(pred: (A) ⇒ Boolean): (Repr, Repr)
Partitions this general collection in two general collections according to a predicate.
Partitions this general collection in two general collections according to a predicate.
- pred
the predicate on which to partition.
- returns
a pair of general collections: the first general collection consists of all elements that satisfy the predicate
p
and the second general collection consists of all elements that don't. The relative order of the elements in the resulting general collections may not be preserved.
-
abstract
def
reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1
Reduces the elements of this collection or iterator using the specified associative binary operator.
Reduces the elements of this collection 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
.- op
A binary operator that must be associative.
- returns
The result of applying reduce operator
op
between all the elements if the collection or iterator is nonempty.
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this collection or iterator is empty.
-
abstract
def
reduceLeftOption[B >: A](op: (B, A) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this collection or iterator, going left to right.
Optionally applies a binary operator to all elements of this collection 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 collection or iterator is nonempty,None
otherwise.
- Definition Classes
- GenTraversableOnce
-
abstract
def
reduceOption[A1 >: A](op: (A1, A1) ⇒ A1): Option[A1]
Reduces the elements of this collection or iterator, if any, using the specified associative binary operator.
Reduces the elements of this collection 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
.- 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.
- Definition Classes
- GenTraversableOnce
-
abstract
def
reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this collection or iterator, going right to left.
Applies a binary operator to all elements of this collection 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 collection or iterator, going right to left:op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where
x1, ..., xn
are the elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this collection or iterator is empty.
-
abstract
def
reduceRightOption[B >: A](op: (A, B) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this collection or iterator, going right to left.
Optionally applies a binary operator to all elements of this collection 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 collection or iterator is nonempty,None
otherwise.
- Definition Classes
- GenTraversableOnce
- abstract def repr: Repr
-
abstract
def
scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Repr, B, That]): That
Computes a prefix scan of the elements of the collection.
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
- op
the associative operator for the scan
- cbf
combiner factory which provides a combiner
- returns
a new general collection containing the prefix scan of the elements in this general collection
-
abstract
def
scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That
Produces a collection containing cumulative results of applying the operator going left to right.
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 the new element typeB
.- returns
collection with intermediate results
-
abstract
def
scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That
Produces a collection containing cumulative results of applying the operator going right to left.
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:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
- 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 the new element typeB
.- returns
collection with intermediate results
- Annotations
- @migration
- Migration
(Changed in version 2.9.0) The behavior of
scanRight
has changed. The previous behavior can be reproduced with scanRight.reverse.
-
abstract
def
seq: TraversableOnce[A]
- Definition Classes
- Parallelizable
-
abstract
def
size: Int
The size of this general collection.
The size of this general collection.
Note: will not terminate for infinite-sized collections.
- returns
the number of elements in this general collection.
- Definition Classes
- GenTraversableLike → GenTraversableOnce
-
abstract
def
slice(unc_from: Int, unc_until: Int): Repr
Selects an interval of elements.
Selects an interval of elements. The returned collection is made up of all elements
x
which satisfy the invariant:from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
- unc_from
the lowest index to include from this general collection.
- unc_until
the lowest index to EXCLUDE from this general collection.
- returns
a general collection containing the elements greater than or equal to index
from
extending up to (but not including) indexuntil
of this general collection.
-
abstract
def
span(pred: (A) ⇒ Boolean): (Repr, Repr)
Splits this general collection into a prefix/suffix pair according to a predicate.
Splits this general 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 predicatep
does not cause any side-effects.Note: might return different results for different runs, unless the underlying collection type is ordered.
- pred
the test predicate
- returns
a pair consisting of the longest prefix of this general collection whose elements all satisfy
p
, and the rest of this general collection.
-
abstract
def
splitAt(n: Int): (Repr, Repr)
Splits this general collection into two at a given position.
Splits this general 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 general collections consisting of the first
n
elements of this general collection, and the other elements.
-
abstract
def
stringPrefix: String
Defines the prefix of this object's
toString
representation.Defines the prefix of this object's
toString
representation.- returns
a string representation which starts the result of
toString
applied to this general collection. By default the string prefix is the simple name of the collection class general collection.
-
abstract
def
tail: Repr
Selects all elements except the first.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
a general collection consisting of all elements of this general collection except the first one.
- Exceptions thrown
UnsupportedOperationException
if the general collection is empty.
-
abstract
def
take(n: Int): Repr
Selects first n elements.
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 general collection.
- returns
a general collection consisting only of the first
n
elements of this general collection, or else the whole general collection, if it has less thann
elements. Ifn
is negative, returns an empty general collection.
-
abstract
def
takeWhile(pred: (A) ⇒ Boolean): Repr
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- pred
The predicate used to test elements.
- returns
the longest prefix of this general collection whose elements all satisfy the predicate
p
.
-
abstract
def
toBuffer[A1 >: A]: Buffer[A1]
Uses the contents of this collection or iterator to create a new mutable buffer.
Uses the contents of this collection or iterator to create a new mutable buffer.
Note: will not terminate for infinite-sized collections.
- returns
a buffer containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toIndexedSeq: immutable.IndexedSeq[A]
Converts this collection or iterator to an indexed sequence.
Converts this collection or iterator to an indexed sequence.
Note: will not terminate for infinite-sized collections.
- returns
an indexed sequence containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toIterable: GenIterable[A]
Converts this collection or iterator to an iterable collection.
Converts this collection or iterator to an iterable collection. Note that the choice of target
Iterable
is lazy in this default implementation as thisTraversableOnce
may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).Note: will not terminate for infinite-sized collections.
- returns
an
Iterable
containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toIterator: Iterator[A]
Returns an Iterator over the elements in this collection or iterator.
Returns an Iterator over the elements in this collection or iterator. Will return the same Iterator if this instance is already an Iterator.
Note: will not terminate for infinite-sized collections.
- returns
an Iterator containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toList: List[A]
Converts this collection or iterator to a list.
Converts this collection or iterator to a list.
Note: will not terminate for infinite-sized collections.
- returns
a list containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toSeq: GenSeq[A]
Converts this collection or iterator to a sequence.
Converts this collection or iterator to a sequence. As with
toIterable
, it's lazy in this default implementation, as thisTraversableOnce
may be lazy and unevaluated.Note: will not terminate for infinite-sized collections.
- returns
a sequence containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toSet[A1 >: A]: GenSet[A1]
Converts this collection or iterator to a set.
Converts this collection or iterator to a set.
Note: will not terminate for infinite-sized collections.
- returns
a set containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toStream: Stream[A]
Converts this collection or iterator to a stream.
Converts this collection or iterator to a stream.
- returns
a stream containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toTraversable: GenTraversable[A]
Converts this collection or iterator to an unspecified Traversable.
Converts this collection or iterator to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
- returns
a Traversable containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toVector: Vector[A]
Converts this collection or iterator to a Vector.
Converts this collection or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
- returns
a vector containing all elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
-
abstract
def
/:[B](z: B)(op: (B, A) ⇒ B): B
Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.
Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.
Note:
/:
is alternate syntax forfoldLeft
;z /: xs
is the same asxs foldLeft z
.Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (5 /: a)(_+_) b: Int = 15 scala> val c = (5 /: a)((x,y) => x + y) c: Int = 15
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 collection or iterator, going left to right with the start valuez
on the left:op(...op(op(z, x_1), x_2), ..., x_n)
where
x1, ..., xn
are the elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.10) Use foldLeft instead of /:
-
abstract
def
:\[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.
Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.
Note:
:\
is alternate syntax forfoldRight
;xs :\ z
is the same asxs 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.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (a :\ 5)(_+_) b: Int = 15 scala> val c = (a :\ 5)((x,y) => x + y) c: Int = 15
- 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 collection or iterator, going right to left with the start valuez
on the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xn
are the elements of this collection or iterator.
- Definition Classes
- GenTraversableOnce
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.10) Use foldRight instead of :\
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- Any
-
final
def
##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- Any
-
def
+(other: String): String
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to any2stringadd[GenTraversableLike[A, Repr]] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
-
def
->[B](y: B): (GenTraversableLike[A, Repr], B)
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to ArrowAssoc[GenTraversableLike[A, Repr]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
-
final
def
==(arg0: Any): Boolean
Test two objects for equality.
Test two objects for equality. The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
-
final
def
asInstanceOf[T0]: T0
Cast the receiver object to be of type
T0
.Cast the receiver object to be of type
T0
.Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression
1.asInstanceOf[String]
will throw aClassCastException
at runtime, while the expressionList(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver object is not an instance of the erasure of typeT0
.
-
abstract
def
collect[B](pf: PartialFunction[A, B]): GenTraversable[B]
[use case] Builds a new collection by applying a partial function to all elements of this general collection on which the function is defined.
[use case]Builds a new collection by applying a partial function to all elements of this general collection on which the function is defined.
- B
the element type of the returned collection.
- pf
the partial function which filters and maps the general collection.
- returns
a new general 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.
Full Signatureabstract def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That
-
abstract
def
copyToArray(xs: Array[A], start: Int, len: Int): Unit
[use case] Copies the elements of this general collection to an array.
[use case]Copies the elements of this general collection to an array. Fills the given array
xs
with at mostlen
elements of this general collection, starting at positionstart
. Copying will stop once either the end of the current general collection is reached, or the end of the target array is reached, orlen
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
- GenTraversableOnce
-
abstract
def
copyToArray(xs: Array[A], start: Int): Unit
[use case] Copies the elements of this general collection to an array.
[use case]Copies the elements of this general collection to an array. Fills the given array
xs
with values of this general collection, beginning at indexstart
. Copying will stop once either the end of the current general 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
- GenTraversableOnce
-
abstract
def
copyToArray(xs: Array[A]): Unit
[use case] Copies the elements of this general collection to an array.
[use case]Copies the elements of this general collection to an array. Fills the given array
xs
with values of this general collection. Copying will stop once either the end of the current general 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
- GenTraversableOnce
-
def
ensuring(cond: (GenTraversableLike[A, Repr]) ⇒ Boolean, msg: ⇒ Any): GenTraversableLike[A, Repr]
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to Ensuring[GenTraversableLike[A, Repr]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: (GenTraversableLike[A, Repr]) ⇒ Boolean): GenTraversableLike[A, Repr]
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to Ensuring[GenTraversableLike[A, Repr]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean, msg: ⇒ Any): GenTraversableLike[A, Repr]
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to Ensuring[GenTraversableLike[A, Repr]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean): GenTraversableLike[A, Repr]
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to Ensuring[GenTraversableLike[A, Repr]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
equals(arg0: Any): Boolean
Compares the receiver object (
this
) with the argument object (that
) for equivalence.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)
returnstrue
) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)
).- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
- It is reflexive: for any instance
-
abstract
def
flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): GenTraversable[B]
[use case] Builds a new collection by applying a function to all elements of this general collection and using the elements of the resulting collections.
[use case]Builds a new collection by applying a function to all elements of this general collection and using the elements of the resulting collections.
For example:
def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")
The type of the resulting collection is guided by the static type of general collection. This might cause unexpected results sometimes. For example:
// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet) // lettersOf will return a Set[Char], not a Seq def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq) // xs will be an Iterable[Int] val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2) // ys will be a Map[Int, Int] val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new general collection resulting from applying the given collection-valued function
f
to each element of this general collection and concatenating the results.
Full Signatureabstract def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That
-
abstract
def
foreach(f: (A) ⇒ Unit): Unit
[use case] Applies a function
f
to all elements of this general collection.[use case]Applies a function
f
to all elements of this general collection.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.
- Definition Classes
- GenTraversableLike → GenTraversableOnce
Full Signatureabstract def foreach[U](f: (A) ⇒ U): Unit
-
def
formatted(fmtstr: String): String
Returns string formatted according to given
format
string.Returns string formatted according to given
format
string. Format strings are as forString.format
(@see java.lang.String.format).- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to StringFormat[GenTraversableLike[A, Repr]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @inline()
-
def
hashCode(): Int
Calculate a hash code value for the object.
Calculate a hash code value for the object.
The default hashing algorithm is platform dependent.
Note that it is allowed for two objects to have identical hash codes (
o1.hashCode.equals(o2.hashCode)
) yet not be equal (o1.equals(o2)
returnsfalse
). A degenerate implementation could always return0
. However, it is required that if two objects are equal (o1.equals(o2)
returnstrue
) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)
). Therefore, when overriding this method, be sure to verify that the behavior is consistent with theequals
method.- returns
the hash code value for this object.
- Definition Classes
- Any
-
final
def
isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is
T0
.Test whether the dynamic type of the receiver object is
T0
.Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression
1.isInstanceOf[String]
will returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
-
abstract
def
map[B](f: (A) ⇒ B): GenTraversable[B]
[use case] Builds a new collection by applying a function to all elements of this general collection.
[use case]Builds a new collection by applying a function to all elements of this general collection.
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new general collection resulting from applying the given function
f
to each element of this general collection and collecting the results.
Full Signatureabstract def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That
-
abstract
def
max: A
[use case] Finds the largest element.
[use case]Finds the largest element.
- returns
the largest element of this general collection.
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this general collection is empty.
Full Signatureabstract def max[A1 >: A](implicit ord: Ordering[A1]): A
-
abstract
def
maxBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the largest value measured by function f.
[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 general collection with the largest value measured by function f.
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this general collection is empty.
Full Signatureabstract def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
abstract
def
min: A
[use case] Finds the smallest element.
[use case]Finds the smallest element.
- returns
the smallest element of this general collection
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this general collection is empty.
Full Signatureabstract def min[A1 >: A](implicit ord: Ordering[A1]): A
-
abstract
def
minBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the smallest value measured by function f.
[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 general collection with the smallest value measured by function f.
- Definition Classes
- GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this general collection is empty.
Full Signatureabstract def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
def
par: ParIterable[A]
Returns a parallel implementation of this collection.
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
ormutable.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
-
abstract
def
product: A
[use case] Multiplies up the elements of this collection.
[use case]Multiplies up the elements of this collection.
- returns
the product of all elements in this general collection of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the general collection and as result type ofproduct
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- GenTraversableOnce
Full Signatureabstract def product[A1 >: A](implicit num: Numeric[A1]): A1
-
def
sizeHintIfCheap: Int
The size of this collection or iterator, if it can be cheaply computed
The size of this collection or iterator, if it can be cheaply computed
- returns
the number of elements in this collection or iterator, or -1 if the size cannot be determined cheaply
- Attributes
- protected[collection]
- Definition Classes
- GenTraversableOnce
-
abstract
def
sum: A
[use case] Sums up the elements of this collection.
[use case]Sums up the elements of this collection.
- returns
the sum of all elements in this general collection of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the general collection and as result type ofsum
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- GenTraversableOnce
Full Signatureabstract def sum[A1 >: A](implicit num: Numeric[A1]): A1
-
abstract
def
to[Col[_]]: Col[A]
[use case] Converts this general collection into another by copying all elements.
[use case]Converts this general collection into another by copying all elements.
Note: will not terminate for infinite-sized collections.
- Col
The collection type to build.
- returns
a new collection containing all elements of this general collection.
- Definition Classes
- GenTraversableOnce
Full Signatureabstract def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]
-
abstract
def
toArray: Array[A]
[use case] Converts this general collection to an array.
[use case]Converts this general collection to an array.
Note: will not terminate for infinite-sized collections.
- returns
an array containing all elements of this general collection. An
ClassTag
must be available for the element type of this general collection.
- Definition Classes
- GenTraversableOnce
-
abstract
def
toMap[T, U]: Map[T, U]
[use case] Converts this general collection to a map.
[use case]Converts this general 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 general collection.
- Definition Classes
- GenTraversableOnce
-
def
toParArray: ParArray[T]
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to CollectionsHaveToParArray[GenTraversableLike[A, Repr], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (GenTraversableLike[A, Repr]) ⇒ GenTraversableOnce[T] is in scope.
- Definition Classes
- CollectionsHaveToParArray
-
def
toString(): String
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
- returns
a string representation of the object.
- Definition Classes
- Any
-
def
→[B](y: B): (GenTraversableLike[A, Repr], B)
- Implicit
- This member is added by an implicit conversion from GenTraversableLike[A, Repr] to ArrowAssoc[GenTraversableLike[A, Repr]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.collection.parallel.immutable
- Immutable, parallel data-structures such asParVector
,ParRange
,ParHashMap
orParHashSet
scala.collection.parallel.mutable
- Mutable, parallel data-structures such asParArray
,ParHashMap
,ParTrieMap
orParHashSet
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.