sealed abstract class Stream[+A] extends AbstractSeq[A] with LinearSeq[A] with GenericTraversableTemplate[A, Stream] with LinearSeqOptimized[A, Stream[A]] with Serializable
The class Stream
implements lazy lists where elements
are only evaluated when they are needed. Here is an example:
import scala.math.BigInt object Main extends App { lazy val fibs: Stream[BigInt] = BigInt(0) #:: BigInt(1) #:: fibs.zip(fibs.tail).map { n => n._1 + n._2 } fibs take 5 foreach println } // prints // // 0 // 1 // 1 // 2 // 3
The Stream
class also employs memoization such that previously computed
values are converted from Stream
elements to concrete values of type A
.
To illustrate, we will alter body of the fibs
value above and take some
more values:
import scala.math.BigInt object Main extends App { lazy val fibs: Stream[BigInt] = BigInt(0) #:: BigInt(1) #:: fibs.zip( fibs.tail).map(n => { println("Adding %d and %d".format(n._1, n._2)) n._1 + n._2 }) fibs take 5 foreach println fibs take 6 foreach println } // prints // // 0 // 1 // Adding 0 and 1 // 1 // Adding 1 and 1 // 2 // Adding 1 and 2 // 3 // And then prints // // 0 // 1 // 1 // 2 // 3 // Adding 2 and 3 // 5
There are a number of subtle points to the above example.
- The definition of
fibs
is aval
not a method. The memoization of theStream
requires us to have somewhere to store the information and aval
allows us to do that. - While the
Stream
is actually being modified during access, this does not change the notion of its immutability. Once the values are memoized they do not change and values that have yet to be memoized still "exist", they simply haven't been realized yet. - One must be cautious of memoization; you can very quickly eat up large
amounts of memory if you're not careful. The reason for this is that the
memoization of the
Stream
creates a structure much like scala.collection.immutable.List. So long as something is holding on to the head, the head holds on to the tail, and so it continues recursively. If, on the other hand, there is nothing holding on to the head (e.g. we useddef
to define theStream
) then once it is no longer being used directly, it disappears. - Note that some operations, including drop, dropWhile,
flatMap or collect may process a large number of intermediate
elements before returning. These necessarily hold onto the head, since
they are methods on
Stream
, and a stream holds its own head. For computations of this sort where memoization is not desired, useIterator
when possible.
// For example, let's build the natural numbers and do some silly iteration // over them. // We'll start with a silly iteration def loop(s: String, i: Int, iter: Iterator[Int]): Unit = { // Stop after 200,000 if (i < 200001) { if (i % 50000 == 0) println(s + i) loop(s, iter.next, iter) } } // Our first Stream definition will be a val definition val stream1: Stream[Int] = { def loop(v: Int): Stream[Int] = v #:: loop(v + 1) loop(0) } // Because stream1 is a val, everything that the iterator produces is held // by virtue of the fact that the head of the Stream is held in stream1 val it1 = stream1.iterator loop("Iterator1: ", it1.next, it1) // We can redefine this Stream such that all we have is the Iterator left // and allow the Stream to be garbage collected as required. Using a def // to provide the Stream ensures that no val is holding onto the head as // is the case with stream1 def stream2: Stream[Int] = { def loop(v: Int): Stream[Int] = v #:: loop(v + 1) loop(0) } val it2 = stream2.iterator loop("Iterator2: ", it2.next, it2) // And, of course, we don't actually need a Stream at all for such a simple // problem. There's no reason to use a Stream if you don't actually need // one. val it3 = new Iterator[Int] { var i = -1 def hasNext = true def next(): Int = { i += 1; i } } loop("Iterator3: ", it3.next, it3)
- The fact that
tail
works at all is of interest. In the definition offibs
we have an initial(0, 1, Stream(...))
sotail
is deterministic. If we definedfibs
such that only0
were concretely known then the act of determiningtail
would require the evaluation oftail
which would cause an infinite recursion and stack overflow. If we define a definition where the tail is not initially computable then we're going to have an infinite recursion:
// The first time we try to access the tail we're going to need more // information which will require us to recurse, which will require us to // recurse, which... lazy val sov: Stream[Vector[Int]] = Vector(0) #:: sov.zip(sov.tail).map { n => n._1 ++ n._2 }
The definition of fibs
above creates a larger number of objects than
necessary depending on how you might want to implement it. The following
implementation provides a more "cost effective" implementation due to the
fact that it has a more direct route to the numbers themselves:
lazy val fib: Stream[Int] = { def loop(h: Int, n: Int): Stream[Int] = h #:: loop(n, h + n) loop(1, 1) }
Note that mkString
forces evaluation of a Stream
, but addString
does
not. In both cases, a Stream
that is or ends in a cycle
(e.g. lazy val s: Stream[Int] = 0 #:: s
) will convert additional trips
through the cycle to ...
. Additionally, addString
will display an
un-memoized tail as ?
.
- A
the type of the elements contained in this stream.
- Self Type
- Stream[A]
- Source
- Stream.scala
- Version
1.1 08/08/03
- Since
2.8
- See also
"Scala's Collection Library overview" section on
Streams
for more information.
- Alphabetic
- By Inheritance
- Stream
- Serializable
- Serializable
- LinearSeqOptimized
- LinearSeq
- LinearSeq
- LinearSeqLike
- Seq
- Iterable
- Traversable
- Immutable
- AbstractSeq
- Seq
- SeqLike
- GenSeq
- GenSeqLike
- PartialFunction
- Function1
- AbstractIterable
- Iterable
- IterableLike
- Equals
- GenIterable
- GenIterableLike
- AbstractTraversable
- Traversable
- GenTraversable
- GenericTraversableTemplate
- TraversableLike
- GenTraversableLike
- Parallelizable
- TraversableOnce
- GenTraversableOnce
- FilterMonadic
- HasNewBuilder
- AnyRef
- Any
- by CollectionsHaveToParArray
- by MonadOps
- by consWrapper
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- by alternateImplicit
- Hide All
- Show All
- Public
- All
Type Members
-
class
WithFilter
extends FilterMonadic[A, Repr]
A class supporting filtered operations.
A class supporting filtered operations. Instances of this class are returned by method
withFilter
.- Definition Classes
- TraversableLike
-
type
Self = Stream[A]
The type implementing this traversable
The type implementing this traversable
- Attributes
- protected[this]
- Definition Classes
- TraversableLike
Abstract Value Members
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
- AnyRef → 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
- AnyRef → Any
-
def
#::(hd: A): Stream[A]
Construct a stream consisting of a given first element followed by elements from a lazily evaluated Stream.
Construct a stream consisting of a given first element followed by elements from a lazily evaluated Stream.
- Implicit
- This member is added by an implicit conversion from Stream[A] to ConsWrapper[A] performed by method consWrapper in scala.collection.immutable.Stream.
- Definition Classes
- ConsWrapper
-
def
#:::(prefix: Stream[A]): Stream[A]
Construct a stream consisting of the concatenation of the given stream and a lazily evaluated Stream.
Construct a stream consisting of the concatenation of the given stream and a lazily evaluated Stream.
- Implicit
- This member is added by an implicit conversion from Stream[A] to ConsWrapper[A] performed by method consWrapper in scala.collection.immutable.Stream.
- Definition Classes
- ConsWrapper
-
def
+(other: String): String
- Implicit
- This member is added by an implicit conversion from Stream[A] to any2stringadd[Stream[A]] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
-
def
++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That
Create a new stream which contains all elements of this stream followed by all elements of Traversable
that
.Create a new stream which contains all elements of this stream followed by all elements of Traversable
that
.- B
The element type of the returned collection.That
- 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 scala.collection.GenTraversableOnce to be concatenated to this
Stream
.- 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 containing the result of concatenating
this
withthat
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
- Note
This method doesn't cause the
,Stream
to be fully realized but it should be noted that using the++
operator from another collection type could cause infinite realization of aStream
. For example, referring to the definition offibs
in the preamble, the following would never return:List(BigInt(12)) ++ fibs
.It's subtle why this works. We know that if the target type of the scala.collection.mutable.Builder
That
is either aStream
, or one of its supertypes, or undefined, thenStreamBuilder
will be chosen for the implicit. We recognize that fact and optimize to get more laziness.
-
def
++:[B >: A, That](that: collection.Traversable[B])(implicit bf: CanBuildFrom[Stream[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.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:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
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, butTraversable
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.- 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 traversable collection followed by all elements ofthat
.
- Definition Classes
- TraversableLike
-
def
++:[B](that: TraversableOnce[B]): Stream[B]
[use case] As with
++
, returns a new collection containing the elements from the left operand followed by the elements from the right operand.[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:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
- B
the element type of the returned collection.
- that
the traversable to append.
- returns
a new stream which contains all elements of this stream followed by all elements of
that
.
- Definition Classes
- TraversableLike
Full Signaturedef ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
+:(elem: A): Stream[A]
[use case] A copy of the stream with an element prepended.
[use case]A copy of the stream with an element prepended.
Note that :-ending operators are right associative (see example). A mnemonic for
+:
vs.:+
is: the COLon goes on the COLlection side.Also, the original stream is not modified, so you will want to capture the result.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = 2 +: x y: List[Int] = List(2, 1) scala> println(x) List(1)
- elem
the prepended element
- returns
a new stream consisting of
elem
followed by all elements of this stream.
- Definition Classes
- Stream → SeqLike → GenSeqLike
Full Signaturedef +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
->[B](y: B): (Stream[A], B)
- Implicit
- This member is added by an implicit conversion from Stream[A] to ArrowAssoc[Stream[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
-
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.
Applies a binary operator to a start value and all elements of this traversable 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 traversable 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 traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
:+(elem: A): Stream[A]
[use case] A copy of this stream with an element appended.
[use case]A copy of this stream with an element appended.
A mnemonic for
+:
vs.:+
is: the COLon goes on the COLlection side.Note: will not terminate for infinite-sized collections.
Example:
scala> val a = List(1) a: List[Int] = List(1) scala> val b = a :+ 2 b: List[Int] = List(1, 2) scala> println(a) List(1)
- elem
the appended element
- returns
a new stream consisting of all elements of this stream followed by
elem
.
- Definition Classes
- SeqLike → GenSeqLike
Full Signaturedef :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
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.
Applies a binary operator to all elements of this traversable 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 traversable 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 traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
final
def
==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.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
- AnyRef → Any
-
def
addString(b: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder
Write all defined elements of this iterable into given string builder.
Write all defined elements of this iterable into given string builder. The written text begins with the string
start
and is finished by the stringend
. Inside, the string representations of defined elements (w.r.t. the methodtoString()
) are separated by the stringsep
. The method will not force evaluation of undefined elements. A tail of such elements will be represented by a"?"
instead. A cyclic stream is represented by a"..."
at the point where the cycle repeats.- b
The collection.mutable.StringBuilder factory to which we need to add the string elements.
- start
The prefix of the resulting string (e.g. "Stream(")
- sep
The separator between elements of the resulting string (e.g. ",")
- end
The end of the resulting string (e.g. ")")
- returns
The original collection.mutable.StringBuilder containing the resulting string.
- Definition Classes
- Stream → TraversableOnce
-
def
addString(b: StringBuilder): StringBuilder
Appends all elements of this traversable or iterator to a string builder.
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:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> val h = a.addString(b) h: StringBuilder = 1234
- b
the string builder to which elements are appended.
- returns
the string builder
b
to which elements were appended.
- Definition Classes
- TraversableOnce
-
def
addString(b: StringBuilder, sep: String): StringBuilder
Appends all elements of this traversable or iterator to a string builder using a separator string.
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 stringsep
.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
- b
the string builder to which elements are appended.
- sep
the separator string.
- returns
the string builder
b
to which elements were appended.
- Definition Classes
- 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.
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 traversable 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
- TraversableOnce → GenTraversableOnce
-
def
andThen[C](k: (A) ⇒ C): PartialFunction[Int, C]
Composes this partial function with a transformation function that gets applied to results of this partial function.
Composes this partial function with a transformation function that gets applied to results of this partial function.
- C
the result type of the transformation function.
- k
the transformation function
- returns
a partial function with the same domain as this partial function, which maps arguments
x
tok(this(x))
.
- Definition Classes
- PartialFunction → Function1
-
def
append[B >: A](rest: ⇒ TraversableOnce[B]): Stream[B]
The stream resulting from the concatenation of this stream with the argument stream.
The stream resulting from the concatenation of this stream with the argument stream.
- rest
The stream that gets appended to this stream
- returns
The stream containing elements of this stream and the traversable object.
-
def
apply(n: Int): A
Selects an element by its index in the sequence.
Selects an element by its index in the sequence. Note: the execution of
apply
may take time proportional to the index value.- returns
the element of this sequence at index
idx
, where0
indicates the first element.
- Definition Classes
- LinearSeqOptimized → SeqLike → GenSeqLike
- Exceptions thrown
IndexOutOfBoundsException
ifidx
does not satisfy0 <= idx < length
.
-
def
applyOrElse[A1 <: Int, B1 >: A](x: A1, default: (A1) ⇒ B1): B1
Applies this partial function to the given argument when it is contained in the function domain.
Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.
Note that expression
pf.applyOrElse(x, default)
is equivalent toif(pf isDefinedAt x) pf(x) else default(x)
except that
applyOrElse
method can be implemented more efficiently. For all partial function literals the compiler generates anapplyOrElse
implementation which avoids double evaluation of pattern matchers and guards. This makesapplyOrElse
the basis for the efficient implementation for many operations and scenarios, such as:- combining partial functions into
orElse
/andThen
chains does not lead to excessiveapply
/isDefinedAt
evaluation lift
andunlift
do not evaluate source functions twice on each invocationrunWith
allows efficient imperative-style combining of partial functions with conditionally applied actions
For non-literal partial function classes with nontrivial
isDefinedAt
method it is recommended to overrideapplyOrElse
with custom implementation that avoids doubleisDefinedAt
evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.- x
the function argument
- default
the fallback function
- returns
the result of this function or fallback function application.
- Definition Classes
- PartialFunction
- Since
2.10
- combining partial functions into
-
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
.
-
def
canEqual(that: Any): Boolean
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
- that
The object with which this iterable collection should be compared
- returns
true
, if this iterable collection can possibly equalthat
,false
otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.
- Definition Classes
- IterableLike → Equals
-
def
clone(): AnyRef
Create a copy of the receiver object.
-
final
def
collect[B](pf: PartialFunction[A, B]): Stream[B]
[use case] Builds a new collection by applying a partial function to all elements of this stream on which the function is defined.
[use case]Builds a new collection by applying a partial function to all elements of this stream on which the function is defined.
- B
the element type of the returned collection.
- pf
the partial function which filters and maps the stream.
- returns
a new stream 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.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
Full Signaturefinal def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
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.
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.
- Definition Classes
- TraversableOnce
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Example: -
def
combinations(n: Int): Iterator[Stream[A]]
Iterates over combinations.
Iterates over combinations. A _combination_ of length
n
is a subsequence of the original sequence, with the elements taken in order. Thus,"xy"
and"yy"
are both length-2 combinations of"xyy"
, but"yx"
is not. If there is more than one way to generate the same subsequence, only one will be returned.For example,
"xyyy"
has three different ways to generate"xy"
depending on whether the first, second, or third"y"
is selected. However, since all are identical, only one will be chosen. Which of the three will be taken is an implementation detail that is not defined.- returns
An Iterator which traverses the possible n-element combinations of this sequence.
- Definition Classes
- SeqLike
"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)
Example: -
def
companion: GenericCompanion[Stream]
The factory companion object that builds instances of class
Stream
.The factory companion object that builds instances of class
Stream
. (or itsIterable
superclass where classStream
is not aSeq
.)- Definition Classes
- Stream → LinearSeq → LinearSeq → Seq → Iterable → Traversable → Seq → GenSeq → Iterable → GenIterable → Traversable → GenTraversable → GenericTraversableTemplate
-
def
compose[A](g: (A) ⇒ Int): (A) ⇒ A
Composes two instances of Function1 in a new Function1, with this function applied last.
Composes two instances of Function1 in a new Function1, with this function applied last.
- A
the type to which function
g
can be applied- g
a function A => T1
- returns
a new function
f
such thatf(x) == apply(g(x))
- Definition Classes
- Function1
- Annotations
- @unspecialized()
-
def
contains[A1 >: A](elem: A1): Boolean
Tests whether this sequence contains a given value as an element.
Tests whether this sequence contains a given value as an element.
Note: may not terminate for infinite-sized collections.
- elem
the element to test.
- returns
true
if this sequence has an element that is equal (as determined by==
) toelem
,false
otherwise.
- Definition Classes
- LinearSeqOptimized → SeqLike
-
def
containsSlice[B](that: GenSeq[B]): Boolean
Tests whether this sequence contains a given sequence as a slice.
Tests whether this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
the sequence to test
- returns
true
if this sequence contains a slice with the same elements asthat
, otherwisefalse
.
- Definition Classes
- SeqLike
-
def
copyToArray(xs: Array[A], start: Int, len: Int): Unit
[use case] Copies the elements of this stream to an array.
[use case]Copies the elements of this stream to an array. Fills the given array
xs
with at mostlen
elements of this stream, starting at positionstart
. Copying will stop once either the end of the current stream 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
- IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
copyToArray(xs: Array[A]): Unit
[use case] Copies the elements of this stream to an array.
[use case]Copies the elements of this stream to an array. Fills the given array
xs
with values of this stream. Copying will stop once either the end of the current stream 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
-
def
copyToArray(xs: Array[A], start: Int): Unit
[use case] Copies the elements of this stream to an array.
[use case]Copies the elements of this stream to an array. Fills the given array
xs
with values of this stream, beginning at indexstart
. Copying will stop once either the end of the current stream 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
-
def
copyToBuffer[B >: A](dest: Buffer[B]): Unit
Copies all elements of this traversable or iterator to a buffer.
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
-
final
def
corresponds[B](that: GenSeq[B])(p: (A, B) ⇒ Boolean): Boolean
Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.
Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.
- B
the type of the elements of
that
- that
the other sequence
- p
the test predicate, which relates elements from both sequences
- returns
true
if both sequences have the same length andp(x, y)
istrue
for all corresponding elementsx
of this sequence andy
ofthat
, otherwisefalse
.
- Definition Classes
- LinearSeqLike → SeqLike → GenSeqLike
- Annotations
- @tailrec()
-
def
count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the traversable or iterator which satisfy a predicate.
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
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
diff(that: collection.Seq[A]): Stream[A]
[use case] Computes the multiset difference between this stream and another sequence.
[use case]Computes the multiset difference between this stream and another sequence.
Note: will not terminate for infinite-sized collections.
- that
the sequence of elements to remove
- returns
a new stream which contains all elements of this stream except some of occurrences of elements that also appear in
that
. If an element valuex
appears n times inthat
, then the first n occurrences ofx
will not form part of the result, but any following occurrences will.
- Definition Classes
- SeqLike → GenSeqLike
-
def
distinct: Stream[A]
Builds a new stream from this stream in which any duplicates (as determined by
==
) have been removed.Builds a new stream from this stream in which any duplicates (as determined by
==
) have been removed. Among duplicate elements, only the first one is retained in the resultingStream
.- returns
A new
Stream
representing the result of applying distinctness to the originalStream
.
- Definition Classes
- Stream → SeqLike → GenSeqLike
// Creates a Stream where every element is duplicated def naturalsFrom(i: Int): Stream[Int] = i #:: { i #:: naturalsFrom(i + 1) } naturalsFrom(1) take 6 mkString ", " // produces: "1, 1, 2, 2, 3, 3" (naturalsFrom(1) distinct) take 6 mkString ", " // produces: "1, 2, 3, 4, 5, 6"
Example: -
final
def
drop(n: Int): Stream[A]
Selects all elements except first n ones.
Selects all elements except first n ones.
- n
the number of elements to drop from this stream.
- returns
a stream consisting of all elements of this stream except the first
n
ones, or else the empty stream, if this stream has less thann
elements.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike → TraversableLike → GenTraversableLike
- Annotations
- @tailrec()
-
def
dropRight(n: Int): Stream[A]
Selects all elements except last n ones.
Selects all elements except last n ones.
Note: lazily evaluated; will terminate for infinite-sized collections.
- n
The number of elements to take
- returns
a stream consisting of all elements of this stream except the last
n
ones, or else the empty stream, if this stream has less thann
elements.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike
-
def
dropWhile(p: (A) ⇒ Boolean): Stream[A]
Returns the a
Stream
representing the longest suffix of this iterable whose first element does not satisfy the predicatep
.Returns the a
Stream
representing the longest suffix of this iterable whose first element does not satisfy the predicatep
.- p
the test predicate.
- returns
A new
Stream
representing the results of applyingp
to the originalStream
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
// Assume we have a Stream that takes the first 20 natural numbers def naturalsLt50(i: Int): Stream[Int] = i #:: { if (i < 20) naturalsLt50(i * + 1) else Stream.Empty } naturalsLt50(0) dropWhile { _ < 10 } // produces: "10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20"
- Note
This method realizes the entire
Stream
beyond the truth value of the predicatep
.
Example: -
def
endsWith[B](that: GenSeq[B]): Boolean
Tests whether this sequence ends with the given sequence.
Tests whether this sequence ends with the given sequence.
Note: will not terminate for infinite-sized collections.
- that
the sequence to test
- returns
true
if this sequence hasthat
as a suffix,false
otherwise.
- Definition Classes
- SeqLike → GenSeqLike
-
def
ensuring(cond: (Stream[A]) ⇒ Boolean, msg: ⇒ Any): Stream[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to Ensuring[Stream[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: (Stream[A]) ⇒ Boolean): Stream[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to Ensuring[Stream[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean, msg: ⇒ Any): Stream[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to Ensuring[Stream[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean): Stream[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to Ensuring[Stream[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
final
def
eq(arg0: AnyRef): Boolean
Tests whether the argument (
that
) is a reference to the receiver object (this
).Tests whether the argument (
that
) is a reference to the receiver object (this
).The
eq
method implements an equivalence relation on non-null instances ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2
), they should be equal to each other (o1 == o2
) and they should hash to the same value (o1.hashCode == o2.hashCode
).- returns
true
if the argument is a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
- It is consistent: for any non-null instances
-
def
equals(that: Any): Boolean
The equals method for arbitrary sequences.
The equals method for arbitrary sequences. Compares this sequence to some other object.
- that
The object to compare the sequence to
- returns
true
ifthat
is a sequence that has the same elements as this sequence in the same order,false
otherwise
- Definition Classes
- Stream → GenSeqLike → Equals → AnyRef → Any
-
def
exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this sequence.
Tests whether a predicate holds for at least one element of this sequence.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
false
if this sequence is empty, otherwisetrue
if the given predicatep
holds for some of the elements of this sequence, otherwisefalse
- Definition Classes
- LinearSeqOptimized → IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
filter(p: (A) ⇒ Boolean): Stream[A]
Selects all elements of this traversable collection which satisfy a predicate.
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.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
filterNot(p: (A) ⇒ Boolean): Stream[A]
Selects all elements of this traversable collection which do not satisfy a predicate.
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.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the
finalize
method is invoked, as well as the interaction betweenfinalize
and non-local returns and exceptions, are all platform dependent. -
def
find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the sequence satisfying a predicate, if any.
Finds the first element of the sequence satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
an option value containing the first element in the sequence that satisfies
p
, orNone
if none exists.
- Definition Classes
- LinearSeqOptimized → IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
final
def
flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That
Applies the given function
f
to each element of this stream, then concatenates the results.Applies the given function
f
to each element of this stream, then concatenates the results. As withmap
this function does not need to realize the entireStream
but continues to keep it as a lazyStream
.- B
The element type of the returned collection That.
- 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.- f
the function to apply on each element.
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
f(a0) ::: ... ::: f(an)
if this stream is[a0, ..., an]
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike → FilterMonadic
// Let's create a Stream of Vectors, each of which contains the // collection of Fibonacci numbers up to the current value. We // can then 'flatMap' that Stream. val fibVec: Stream[Vector[Int]] = Vector(0) #:: Vector(0, 1) #:: fibVec.zip(fibVec.tail).map(n => { n._2 ++ Vector(n._1.last + n._2.last) }) fibVec take 5 foreach println // prints // Vector(0) // Vector(0, 1) // Vector(0, 1, 1) // Vector(0, 1, 1, 2) // Vector(0, 1, 1, 2, 3) // If we now want to `flatMap` across that stream by adding 10 // we can see what the series turns into: fibVec.flatMap(_.map(_ + 10)) take 15 mkString(", ") // produces: 10, 10, 11, 10, 11, 11, 10, 11, 11, 12, 10, 11, 11, 12, 13
Note: Currently
flatMap
will evaluate as much of the Stream as needed until it finds a non-empty element for the head, which is non-lazy.
Example: -
def
flatten[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Stream[B]
Evaluates and concatenates all elements within the
Stream
into a new flattenedStream
.Evaluates and concatenates all elements within the
Stream
into a new flattenedStream
.- B
The type of the elements of the resulting
Stream
.- asTraversable
an implicit conversion which asserts that the element type of this stream is a
GenTraversable
.- returns
A new
Stream
of typeB
of the flattened elements ofthis
Stream
.
- Definition Classes
- Stream → GenericTraversableTemplate
val sov: Stream[Vector[Int]] = Vector(0) #:: Vector(0, 0) #:: sov.zip(sov.tail).map { n => n._1 ++ n._2 } sov.flatten take 10 mkString ", " // produces: "0, 0, 0, 0, 0, 0, 0, 0, 0, 0"
Example: -
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.
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
.- 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 traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
final
def
foldLeft[B](z: B)(op: (B, A) ⇒ B): B
Stream specialization of foldLeft which allows GC to collect along the way.
Stream specialization of foldLeft which allows GC to collect along the way.
- B
The type of value being accumulated.
- z
The initial value seeded into the function
op
.- op
The operation to perform on successive elements of the
Stream
.- returns
The accumulated value from successive applications of
op
.
- Definition Classes
- Stream → LinearSeqOptimized → TraversableOnce → GenTraversableOnce
- Annotations
- @tailrec()
-
def
foldRight[B](z: B)(op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this sequence and a start value, going right to left.
Applies a binary operator to all elements of this sequence and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
- 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 sequence, 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 sequence. Returnsz
if this sequence is empty.
- Definition Classes
- LinearSeqOptimized → IterableLike → TraversableOnce → GenTraversableOnce
-
def
forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this sequence.
Tests whether a predicate holds for all elements of this sequence.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if this sequence is empty or the given predicatep
holds for all elements of this sequence, otherwisefalse
.
- Definition Classes
- LinearSeqOptimized → IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
force: Stream[A]
Forces evaluation of the whole stream and returns it.
Forces evaluation of the whole stream and returns it.
- returns
The fully realized
Stream
.
- Note
Often we use
Stream
s to represent an infinite set or series. If that's the case for your particularStream
then this function will never return and will probably crash the VM with anOutOfMemory
exception. This function will not hang on a finite cycle, however.
-
final
def
foreach[U](f: (A) ⇒ U): Unit
Apply the given function
f
to each element of this linear sequence (while respecting the order of the elements).Apply the given function
f
to each element of this linear sequence (while respecting the order of the elements).- U
the type parameter describing the result of function
f
. This result will always be ignored. TypicallyU
isUnit
, but this is not necessary.- f
The treatment to apply to each element.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike → GenericTraversableTemplate → TraversableLike → GenTraversableLike → TraversableOnce → GenTraversableOnce → FilterMonadic
- Annotations
- @tailrec()
- Note
This function will force the realization of the entire stream unless the
,f
throws an exception.Overridden here as final to trigger tail-call optimization, which replaces 'this' with 'tail' at each iteration. This is absolutely necessary for allowing the GC to collect the underlying stream as elements are consumed.
-
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 Stream[A] to StringFormat[Stream[A]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @inline()
-
def
genericBuilder[B]: Builder[B, Stream[B]]
The generic builder that builds instances of Traversable at arbitrary element types.
The generic builder that builds instances of Traversable at arbitrary element types.
- Definition Classes
- GenericTraversableTemplate
-
final
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
- AnyRef → Any
-
def
groupBy[K](f: (A) ⇒ K): Map[K, Stream[A]]
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
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:
(xs groupBy f)(k) = xs filter (x => f(x) == k)
That is, every key
k
is bound to a traversable collection of those elementsx
for whichf(x)
equalsk
.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
grouped(size: Int): Iterator[Stream[A]]
Partitions elements in fixed size iterable collections.
Partitions elements in fixed size iterable collections.
- size
the number of elements per group
- returns
An iterator producing iterable collections of size
size
, except the last will be less than sizesize
if the elements don't divide evenly.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
grouped
-
def
hasDefiniteSize: Boolean
Tests whether this stream is known to have a finite size.
Tests whether this stream 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
- Stream → TraversableLike → TraversableOnce → GenTraversableOnce
-
def
hashCode(): Int
Hashcodes for
Seq
produce a value from the hashcodes of all the elements of the sequence.Hashcodes for
Seq
produce a value from the hashcodes of all the elements of the sequence.- returns
the hash code value for this object.
- Definition Classes
- LinearSeqLike → GenSeqLike → AnyRef → Any
-
def
head: A
Selects the first element of this iterable collection.
Selects the first element of this iterable collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
the first element of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableLike
- Exceptions thrown
NoSuchElementException
if the iterable collection is empty.
-
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 traversable collection if it is nonempty,
None
if it is empty.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
indexOf(elem: A, from: Int): Int
[use case] Finds index of first occurrence of some value in this stream after or at some start index.
[use case]Finds index of first occurrence of some value in this stream after or at some start index.
Note: may not terminate for infinite-sized collections.
- elem
the element value to search for.
- from
the start index
- returns
the index
>= from
of the first element of this stream that is equal (as determined by==
) toelem
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
-
def
indexOf(elem: A): Int
[use case] Finds index of first occurrence of some value in this stream.
[use case]Finds index of first occurrence of some value in this stream.
Note: may not terminate for infinite-sized collections.
- elem
the element value to search for.
- returns
the index of the first element of this stream that is equal (as determined by
==
) toelem
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
Full Signaturedef indexOf[B >: A](elem: B): Int
-
def
indexOfSlice[B >: A](that: GenSeq[B], from: Int): Int
Finds first index after or at a start index where this sequence contains a given sequence as a slice.
Finds first index after or at a start index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
the sequence to test
- from
the start index
- returns
the first index
>= from
such that the elements of this sequence starting at this index match the elements of sequencethat
, or-1
of no such subsequence exists.
- Definition Classes
- SeqLike
-
def
indexOfSlice[B >: A](that: GenSeq[B]): Int
Finds first index where this sequence contains a given sequence as a slice.
Finds first index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
- that
the sequence to test
- returns
the first index such that the elements of this sequence starting at this index match the elements of sequence
that
, or-1
of no such subsequence exists.
- Definition Classes
- SeqLike
-
def
indexWhere(p: (A) ⇒ Boolean, from: Int): Int
Finds index of the first element satisfying some predicate after or at some start index.
Finds index of the first element satisfying some predicate after or at some start index.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- from
the start index
- returns
the index
>= from
of the first element of this sequence that satisfies the predicatep
, or-1
, if none exists.
- Definition Classes
- LinearSeqOptimized → SeqLike → GenSeqLike
-
def
indexWhere(p: (A) ⇒ Boolean): Int
Finds index of first element satisfying some predicate.
Finds index of first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
the index of the first element of this general sequence that satisfies the predicate
p
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
-
def
indices: Range
Produces the range of all indices of this sequence.
Produces the range of all indices of this sequence.
- returns
a
Range
value from0
to one less than the length of this sequence.
- Definition Classes
- SeqLike
-
def
init: Stream[A]
The stream without its last element.
The stream without its last element.
- returns
A new
Stream
containing everything but the last element. If yourStream
represents an infinite series, this method will not return.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
- Exceptions thrown
UnsupportedOperationException
if the stream is empty.
-
def
inits: Iterator[Stream[A]]
Iterates over the inits of this traversable collection.
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
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Example: -
def
intersect(that: collection.Seq[A]): Stream[A]
[use case] Computes the multiset intersection between this stream and another sequence.
[use case]Computes the multiset intersection between this stream and another sequence.
Note: may not terminate for infinite-sized collections.
- that
the sequence of elements to intersect with.
- returns
a new stream which contains all elements of this stream which also appear in
that
. If an element valuex
appears n times inthat
, then the first n occurrences ofx
will be retained in the result, but any following occurrences will be omitted.
- Definition Classes
- SeqLike → GenSeqLike
-
def
isDefinedAt(x: Int): Boolean
Tests whether this sequence contains given index.
Tests whether this sequence contains given index.
The implementations of methods
apply
andisDefinedAt
turn aSeq[A]
into aPartialFunction[Int, A]
.- returns
true
if this sequence contains an element at positionidx
,false
otherwise.
- Definition Classes
- LinearSeqOptimized → GenSeqLike
-
def
isEmpty: Boolean
Tests whether this sequence is empty.
Tests whether this sequence is empty.
- returns
true
if the sequence contain no elements,false
otherwise.
- Definition Classes
- SeqLike → IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce
-
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
-
final
def
isTraversableAgain: Boolean
Tests whether this traversable collection can be repeatedly traversed.
Tests whether this traversable collection can be repeatedly traversed.
- returns
true
- Definition Classes
- TraversableLike → GenTraversableLike → GenTraversableOnce
-
def
iterator: Iterator[A]
A lazier Iterator than LinearSeqLike's.
A lazier Iterator than LinearSeqLike's.
- returns
the new iterator
- Definition Classes
- Stream → LinearSeqLike → IterableLike → GenIterableLike
-
def
last: A
Selects the last element.
Selects the last element.
- returns
The last element of this sequence.
- Definition Classes
- LinearSeqOptimized → TraversableLike → GenTraversableLike
- Exceptions thrown
NoSuchElementException
If the sequence is empty.
-
def
lastIndexOf(elem: A, end: Int): Int
[use case] Finds index of last occurrence of some value in this stream before or at a given end index.
[use case]Finds index of last occurrence of some value in this stream before or at a given end index.
- elem
the element value to search for.
- end
the end index.
- returns
the index
<= end
of the last element of this stream that is equal (as determined by==
) toelem
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
-
def
lastIndexOf(elem: A): Int
[use case] Finds index of last occurrence of some value in this stream.
[use case]Finds index of last occurrence of some value in this stream.
Note: will not terminate for infinite-sized collections.
- elem
the element value to search for.
- returns
the index of the last element of this stream that is equal (as determined by
==
) toelem
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
Full Signaturedef lastIndexOf[B >: A](elem: B): Int
-
def
lastIndexOfSlice[B >: A](that: GenSeq[B], end: Int): Int
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
- that
the sequence to test
- end
the end index
- returns
the last index
<= end
such that the elements of this sequence starting at this index match the elements of sequencethat
, or-1
of no such subsequence exists.
- Definition Classes
- SeqLike
-
def
lastIndexOfSlice[B >: A](that: GenSeq[B]): Int
Finds last index where this sequence contains a given sequence as a slice.
Finds last index where this sequence contains a given sequence as a slice.
Note: will not terminate for infinite-sized collections.
- that
the sequence to test
- returns
the last index such that the elements of this sequence starting a this index match the elements of sequence
that
, or-1
of no such subsequence exists.
- Definition Classes
- SeqLike
-
def
lastIndexWhere(p: (A) ⇒ Boolean, end: Int): Int
Finds index of last element satisfying some predicate before or at given end index.
Finds index of last element satisfying some predicate before or at given end index.
- p
the predicate used to test elements.
- returns
the index
<= end
of the last element of this sequence that satisfies the predicatep
, or-1
, if none exists.
- Definition Classes
- LinearSeqOptimized → SeqLike → GenSeqLike
-
def
lastIndexWhere(p: (A) ⇒ Boolean): Int
Finds index of last element satisfying some predicate.
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
the index of the last element of this general sequence that satisfies the predicate
p
, or-1
, if none exists.
- Definition Classes
- GenSeqLike
-
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 traversable collection$ if it is nonempty,
None
if it is empty.
- Definition Classes
- TraversableLike → GenTraversableLike
-
def
length: Int
Returns the length of this
Stream
.Returns the length of this
Stream
.- returns
The length of this
Stream
.
- Definition Classes
- Stream → LinearSeqOptimized → SeqLike → GenSeqLike
- Note
In order to compute the length of the
Stream
, it must first be fully realized, which could cause the complete evaluation of an infinite series, assuming that's what yourStream
represents.
-
def
lengthCompare(len: Int): Int
Compares the length of this sequence to a test value.
Compares the length of this sequence to a test value.
- len
the test value that gets compared with the length.
- returns
A value
x
wherex < 0 if this.length < len x == 0 if this.length == len x > 0 if this.length > len
The method as implemented here does not call
length
directly; its running time isO(length min len)
instead ofO(length)
. The method should be overwritten if computinglength
is cheap.
- Definition Classes
- LinearSeqOptimized → SeqLike
-
def
lift: (Int) ⇒ Option[A]
Turns this partial function into a plain function returning an
Option
result.Turns this partial function into a plain function returning an
Option
result.- returns
a function that takes an argument
x
toSome(this(x))
ifthis
is defined forx
, and toNone
otherwise.
- Definition Classes
- PartialFunction
- See also
Function.unlift
-
final
def
map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
Returns the stream resulting from applying the given function
f
to each element of this stream.Returns the stream resulting from applying the given function
f
to each element of this stream. This returns a lazyStream
such that it does not need to be fully realized.- B
The element type of the returned collection That.
- 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.- f
function to apply to each element.
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element typeB
.- returns
f(a0), ..., f(an)
if this sequence isa0, ..., an
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike → FilterMonadic
def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1) naturalsFrom(1).map(_ + 10) take 5 mkString(", ") // produces: "11, 12, 13, 14, 15"
Example: -
def
max: A
[use case] Finds the largest element.
[use case]Finds the largest element.
- returns
the largest element of this stream.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef max[B >: A](implicit cmp: Ordering[B]): A
-
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 stream with the largest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
def
min: A
[use case] Finds the smallest element.
[use case]Finds the smallest element.
- returns
the smallest element of this stream
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef min[B >: A](implicit cmp: Ordering[B]): A
-
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 stream with the smallest value measured by function f.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
def
mkString(start: String, sep: String, end: String): String
Displays all elements of this stream in a string using start, end, and separator strings.
Displays all elements of this stream 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 stream. 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 stream are separated by the stringsep
.
- Definition Classes
- Stream → TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Example: -
def
mkString: String
Displays all elements of this stream in a string.
Displays all elements of this stream in a string.
- returns
a string representation of this stream. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this stream follow each other without any separator string.
- Definition Classes
- Stream → TraversableOnce → GenTraversableOnce
-
def
mkString(sep: String): String
Displays all elements of this stream in a string using a separator string.
Displays all elements of this stream in a string using a separator string.
- sep
the separator string.
- returns
a string representation of this stream. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this stream are separated by the stringsep
.
- Definition Classes
- Stream → TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("|") = "1|2|3"
Example: -
final
def
ne(arg0: AnyRef): Boolean
Equivalent to
!(this eq that)
.Equivalent to
!(this eq that)
.- returns
true
if the argument is not a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
-
def
newBuilder: Builder[A, Stream[A]]
The builder that builds instances of type Traversable[A]
The builder that builds instances of type Traversable[A]
- Attributes
- protected[this]
- Definition Classes
- GenericTraversableTemplate → HasNewBuilder
-
def
nonEmpty: Boolean
Tests whether the traversable or iterator is not empty.
Tests whether the traversable or iterator is not empty.
- returns
true
if the traversable or iterator contains at least one element,false
otherwise.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
final
def
notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Note
not specified by SLS as a member of AnyRef
-
final
def
notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Note
not specified by SLS as a member of AnyRef
-
def
orElse[A1 <: Int, B1 >: A](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
- A1
the argument type of the fallback function
- B1
the result type of the fallback function
- that
the fallback function
- returns
a partial function which has as domain the union of the domains of this partial function and
that
. The resulting partial function takesx
tothis(x)
wherethis
is defined, and tothat(x)
where it is not.
- Definition Classes
- PartialFunction
-
def
padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
Returns a new sequence of given length containing the elements of this sequence followed by zero or more occurrences of given elements.
Returns a new sequence of given length containing the elements of this sequence followed by zero or more occurrences of given elements.
- B
The type of the value to pad with.
- That
The type contained within the resulting
Stream
.- len
The number of elements to pad into the
Stream
.- elem
The value of the type
B
to use for padding.- 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
Stream
representing the collection with values padding off to the end. If yourStream
represents an infinite series, this method will not return.
- Definition Classes
- Stream → SeqLike → GenSeqLike
def naturalsFrom(i: Int): Stream[Int] = i #:: { if (i < 5) naturalsFrom(i + 1) else Stream.Empty } naturalsFrom(1) padTo(10, 0) foreach println // prints // 1 // 2 // 3 // 4 // 5 // 0 // 0 // 0 // 0 // 0
Example: -
def
par: ParSeq[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
-
def
parCombiner: Combiner[A, ParSeq[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
- Seq → SeqLike → Iterable → TraversableLike → Parallelizable
-
def
partition(p: (A) ⇒ Boolean): (Stream[A], Stream[A])
Returns all the elements of this stream that satisfy the predicate
p
returning of scala.Tuple2 ofStream
s obeying the partition predicatep
.Returns all the elements of this stream that satisfy the predicate
p
returning of scala.Tuple2 ofStream
s obeying the partition predicatep
. The order of the elements is preserved.- p
the predicate used to filter the stream.
- returns
the elements of this stream satisfying
p
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1) val parts = naturalsFrom(1) partition { _ % 2 == 0 } parts._1 take 10 mkString ", " // produces: "2, 4, 6, 8, 10, 12, 14, 16, 18, 20" parts._2 take 10 mkString ", " // produces: "1, 3, 5, 7, 9, 11, 13, 15, 17, 19"
Example: -
def
patch(from: Int, that: GenSeq[A], replaced: Int): Stream[A]
[use case] Produces a new stream where a slice of elements in this stream is replaced by another sequence.
[use case]Produces a new stream where a slice of elements in this stream is replaced by another sequence.
- from
the index of the first replaced element
- replaced
the number of elements to drop in the original stream
- returns
a new stream consisting of all elements of this stream except that
replaced
elements starting fromfrom
are replaced bypatch
.
- Definition Classes
- SeqLike → GenSeqLike
Full Signaturedef patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
permutations: Iterator[Stream[A]]
Iterates over distinct permutations.
Iterates over distinct permutations.
- returns
An Iterator which traverses the distinct permutations of this sequence.
- Definition Classes
- SeqLike
"abb".permutations = Iterator(abb, bab, bba)
Example: -
def
prefixLength(p: (A) ⇒ Boolean): Int
Returns the length of the longest prefix whose elements all satisfy some predicate.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
the length of the longest prefix of this general sequence such that every element of the segment satisfies the predicate
p
.
- Definition Classes
- GenSeqLike
-
def
print(sep: String): Unit
Prints elements of this stream one by one, separated by
sep
.Prints elements of this stream one by one, separated by
sep
.- sep
The separator string printed between consecutive elements.
-
def
print(): Unit
Prints elements of this stream one by one, separated by commas.
-
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 stream of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the stream and as result type ofproduct
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef product[B >: A](implicit num: Numeric[B]): B
-
def
reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1
Reduces the elements of this traversable or iterator using the specified associative binary operator.
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
.- 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.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this traversable or iterator is empty.
-
final
def
reduceLeft[B >: A](f: (B, A) ⇒ B): B
Stream specialization of reduceLeft which allows GC to collect along the way.
Stream specialization of reduceLeft which allows GC to collect along the way.
- B
The type of value being accumulated.
- f
The operation to perform on successive elements of the
Stream
.- returns
The accumulated value from successive applications of
f
.
- Definition Classes
- Stream → LinearSeqOptimized → 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.
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.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
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.
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
.- 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
- TraversableOnce → GenTraversableOnce
-
def
reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this sequence, going right to left.
Applies a binary operator to all elements of this sequence, going right to left.
Note: will not terminate for infinite-sized collections.
- B
the result type of the binary operator.
- op
the binary operator.
- returns
the result of inserting
op
between consecutive elements of this sequence, going right to left:op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where
x1, ..., xn
are the elements of this sequence.
- Definition Classes
- LinearSeqOptimized → IterableLike → TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationException
if this sequence is empty.
-
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.
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.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
repr: Stream[A]
The collection of type traversable collection underlying this
TraversableLike
object.The collection of type traversable collection underlying this
TraversableLike
object. By default this is implemented as theTraversableLike
object itself, but this can be overridden.- Definition Classes
- TraversableLike → GenTraversableLike
-
def
reverse: Stream[A]
A list consisting of all elements of this list in reverse order.
A list consisting of all elements of this list in reverse order.
- returns
A new
Stream
containing the representing of the originalStream
in reverse order.
- Definition Classes
- Stream → SeqLike → GenSeqLike
def naturalsFrom(i: Int): Stream[Int] = i #:: { if (i < 5) naturalsFrom(i + 1) else Stream.Empty } (naturalsFrom(1) reverse) foreach println // prints // 5 // 4 // 3 // 2 // 1
- Note
This function must realize the entire
Stream
in order to perform this operation so if yourStream
represents an infinite sequence then this function will never return.
Example: -
def
reverseIterator: Iterator[A]
An iterator yielding elements in reversed order.
An iterator yielding elements in reversed order.
Note: will not terminate for infinite-sized collections.
Note:
xs.reverseIterator
is the same asxs.reverse.iterator
but might be more efficient.- returns
an iterator yielding the elements of this sequence in reversed order
- Definition Classes
- SeqLike
-
def
reverseMap[B](f: (A) ⇒ B): Stream[B]
[use case] Builds a new collection by applying a function to all elements of this stream and collecting the results in reversed order.
[use case]Builds a new collection by applying a function to all elements of this stream and collecting the results in reversed order.
Note: will not terminate for infinite-sized collections.
Note:
xs.reverseMap(f)
is the same asxs.reverse.map(f)
but might be more efficient.- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new stream resulting from applying the given function
f
to each element of this stream and collecting the results in reversed order.
- Definition Classes
- SeqLike → GenSeqLike
Full Signaturedef reverseMap[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
reversed: scala.List[A]
- Attributes
- protected[this]
- Definition Classes
- TraversableOnce
-
def
runWith[U](action: (A) ⇒ U): (Int) ⇒ Boolean
Composes this partial function with an action function which gets applied to results of this partial function.
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression
pf.runWith(action)(x)
is equivalent toif(pf isDefinedAt x) { action(pf(x)); true } else false
except that
runWith
is implemented viaapplyOrElse
and thus potentially more efficient. UsingrunWith
avoids double evaluation of pattern matchers and guards for partial function literals.- action
the action function
- returns
a function which maps arguments
x
toisDefinedAt(x)
. The resulting function runsaction(this(x))
wherethis
is defined.
- Definition Classes
- PartialFunction
- Since
2.10
- See also
applyOrElse
.
-
def
sameElements(that: GenIterable[A]): Boolean
[use case] Checks if the other iterable collection contains the same elements in the same order as this stream.
[use case]Checks if the other iterable collection contains the same elements in the same order as this stream.
Note: will not terminate for infinite-sized collections.
- that
the collection to compare with.
- returns
true
, if both collections contain the same elements in the same order,false
otherwise.
- Definition Classes
- LinearSeqOptimized → IterableLike → GenIterableLike
Full Signaturedef sameElements[B >: A](that: GenIterable[B]): Boolean
-
def
scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Stream[A], 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 traversable collection containing the prefix scan of the elements in this traversable collection
- Definition Classes
- TraversableLike → GenTraversableLike
-
final
def
scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
Create a new stream which contains all intermediate results of applying the operator to subsequent elements left to right.
Create a new stream which contains all intermediate results of applying the operator to subsequent elements left to right.
scanLeft
is analogous tofoldLeft
.- B
the type of the elements in the resulting collection
- That
the actual type of the resulting collection
- z
The initial value for the scan.
- op
A function that will apply operations to successive values in the
Stream
against previous accumulated results.- 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 containing the modifications from the application of
op
.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
- Note
This works because the target type of the scala.collection.mutable.Builder
That
is aStream
.
-
def
scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Stream[A], 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
- 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.
-
def
segmentLength(p: (A) ⇒ Boolean, from: Int): Int
Computes length of longest segment whose elements all satisfy some predicate.
Computes length of longest segment whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- from
the index where the search starts.
- returns
the length of the longest segment of this sequence starting from index
from
such that every element of the segment satisfies the predicatep
.
- Definition Classes
- LinearSeqOptimized → SeqLike → GenSeqLike
-
def
seq: LinearSeq[A]
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.
- returns
a sequential view of the collection.
- Definition Classes
- LinearSeq → LinearSeq → LinearSeqLike → Seq → Seq → GenSeq → GenSeqLike → Iterable → Iterable → GenIterable → Traversable → Traversable → GenTraversable → Parallelizable → TraversableOnce → GenTraversableOnce
-
def
size: Int
The size of this sequence, equivalent to
length
.The size of this sequence, equivalent to
length
.Note: will not terminate for infinite-sized collections.
- returns
the number of elements in this sequence.
- Definition Classes
- SeqLike → GenTraversableLike → TraversableOnce → GenTraversableOnce
-
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[scala.collection]
- Definition Classes
- GenTraversableOnce
-
def
slice(from: Int, until: Int): Stream[A]
A substream starting at index
from
and extending up to (but not including) indexuntil
.A substream starting at index
from
and extending up to (but not including) indexuntil
. This returns aStream
that is lazily evaluated.- from
The index of the first element of the returned subsequence
- until
The index of the element following the returned subsequence
- returns
A new string containing the elements requested from
start
untilend
.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike → TraversableLike → GenTraversableLike
naturalsFrom(0) slice(50, 60) mkString ", " // produces: "50, 51, 52, 53, 54, 55, 56, 57, 58, 59"
Example: -
def
sliding(size: Int, step: Int): Iterator[Stream[A]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
- size
the number of elements per group
- step
the distance between the first elements of successive groups
- returns
An iterator producing iterable collections of size
size
, except the last and the only element will be truncated if there are fewer elements than size.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
sliding
-
def
sliding(size: Int): Iterator[Stream[A]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) "Sliding window" step is 1 by default.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) "Sliding window" step is 1 by default.
- size
the number of elements per group
- returns
An iterator producing iterable collections of size
size
, except the last and the only element will be truncated if there are fewer elements than size.
- Definition Classes
- IterableLike
- See also
scala.collection.Iterator, method
sliding
-
def
sortBy[B](f: (A) ⇒ B)(implicit ord: math.Ordering[B]): Stream[A]
Sorts this
Seq
according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.Sorts this
Seq
according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.- B
the target type of the transformation
f
, and the type where the orderingord
is defined.- f
the transformation function mapping elements to some other domain
B
.- ord
the ordering assumed on domain
B
.- returns
a sequence consisting of the elements of this sequence sorted according to the ordering where
x < y
iford.lt(f(x), f(y))
.
- Definition Classes
- SeqLike
val words = "The quick brown fox jumped over the lazy dog".split(' ') // this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]] words.sortBy(x => (x.length, x.head)) res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
- See also
scala.math.Ordering Note: will not terminate for infinite-sized collections.
Example: -
def
sortWith(lt: (A, A) ⇒ Boolean): Stream[A]
Sorts this sequence according to a comparison function.
Sorts this sequence according to a comparison function.
Note: will not terminate for infinite-sized collections.
The sort is stable. That is, elements that are equal (as determined by
lt
) appear in the same order in the sorted sequence as in the original.- lt
the comparison function which tests whether its first argument precedes its second argument in the desired ordering.
- returns
a sequence consisting of the elements of this sequence sorted according to the comparison function
lt
.
- Definition Classes
- SeqLike
List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) = List("Bob", "John", "Steve", "Tom")
Example: -
def
sorted[B >: A](implicit ord: math.Ordering[B]): Stream[A]
Sorts this sequence according to an Ordering.
Sorts this sequence according to an Ordering.
The sort is stable. That is, elements that are equal (as determined by
lt
) appear in the same order in the sorted sequence as in the original.- ord
the ordering to be used to compare elements.
- returns
a sequence consisting of the elements of this sequence sorted according to the ordering
ord
.
- Definition Classes
- SeqLike
- See also
-
def
span(p: (A) ⇒ Boolean): (Stream[A], Stream[A])
Splits this sequence into a prefix/suffix pair according to a predicate.
Splits this sequence 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.- returns
a pair consisting of the longest prefix of this sequence whose elements all satisfy
p
, and the rest of this sequence.
- Definition Classes
- LinearSeqOptimized → TraversableLike → GenTraversableLike
-
def
splitAt(n: Int): (Stream[A], Stream[A])
Splits this stream into two at a given position.
Splits this stream into two at a given position. Note:
c splitAt n
is equivalent to (but possibly more efficient than)(c take n, c drop n)
.- n
the position at which to split.
- returns
a pair of streams consisting of the first
n
elements of this stream, and the other elements.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
-
def
startsWith[B](that: GenSeq[B], offset: Int): Boolean
Tests whether this sequence contains the given sequence at a given index.
Tests whether this sequence contains the given sequence at a given index.
Note: If the both the receiver object
this
and the argumentthat
are infinite sequences this method may not terminate.- that
the sequence to test
- offset
the index where the sequence is searched.
- returns
true
if the sequencethat
is contained in this sequence at indexoffset
, otherwisefalse
.
- Definition Classes
- SeqLike → GenSeqLike
-
def
startsWith[B](that: GenSeq[B]): Boolean
Tests whether this general sequence starts with the given sequence.
Tests whether this general sequence starts with the given sequence.
- that
the sequence to test
- returns
true
if this collection hasthat
as a prefix,false
otherwise.
- Definition Classes
- GenSeqLike
-
def
stringPrefix: String
Defines the prefix of this object's
toString
representation asStream
.Defines the prefix of this object's
toString
representation asStream
.- returns
a string representation which starts the result of
toString
applied to this stream. By default the string prefix is the simple name of the collection class stream.
- Definition Classes
- Stream → TraversableLike → GenTraversableLike
-
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 stream of numbers of type
Int
. Instead ofInt
, any other typeT
with an implicitNumeric[T]
implementation can be used as element type of the stream and as result type ofsum
. Examples of such types are:Long
,Float
,Double
,BigInt
.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef sum[B >: A](implicit num: Numeric[B]): B
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
tail: Stream[A]
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 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.
-
def
tails: Iterator[Stream[A]]
Iterates over the tails of this traversable collection.
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
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Example: -
def
take(n: Int): Stream[A]
Returns the
n
first elements of thisStream
as anotherStream
, or else the wholeStream
, if it has less thann
elements.Returns the
n
first elements of thisStream
as anotherStream
, or else the wholeStream
, if it has less thann
elements.The result of
take
is, again, aStream
meaning that it also does not make any needless evaluations of theStream
itself, delaying that until the usage of the resultingStream
.- n
the number of elements to take.
- returns
the
n
first elements of this stream.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike → TraversableLike → GenTraversableLike
def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1) scala> naturalsFrom(5) take 5 res1: scala.collection.immutable.Stream[Int] = Stream(5, ?) scala> naturalsFrom(5) take 5 mkString ", " // produces: "5, 6, 7, 8, 9"
Example: -
def
takeRight(n: Int): Stream[A]
Returns the rightmost
n
elements from this iterable.Returns the rightmost
n
elements from this iterable.- n
the number of elements to take
- returns
The last
n
elements from thisStream
.
- Definition Classes
- Stream → IterableLike
- Note
Take serious caution here. If the
Stream
represents an infinite series then this function will not return. The right most elements of an infinite series takes an infinite amount of time to produce.
-
def
takeWhile(p: (A) ⇒ Boolean): Stream[A]
Returns the longest prefix of this
Stream
whose elements satisfy the predicatep
.Returns the longest prefix of this
Stream
whose elements satisfy the predicatep
.- p
the test predicate.
- returns
A new
Stream
representing the values that satisfy the predicatep
.
- Definition Classes
- Stream → LinearSeqOptimized → IterableLike → TraversableLike → GenTraversableLike
+ naturalsFrom(0) takeWhile { _ < 5 } mkString ", " produces: "0, 1, 2, 3, 4"
Example: -
def
thisCollection: collection.LinearSeq[A]
The underlying collection seen as an instance of
.Seq
The underlying collection seen as an instance of
. By default this is implemented as the current collection object itself, but this can be overridden.Seq
- Attributes
- protected[this]
- Definition Classes
- LinearSeqLike → SeqLike → IterableLike → TraversableLike
-
def
to[Col[_]]: Col[A]
[use case] Converts this stream into another by copying all elements.
[use case]Converts this stream 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 stream.
- Definition Classes
- TraversableLike → TraversableOnce → GenTraversableOnce
Full Signaturedef to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]
-
def
toArray: Array[A]
[use case] Converts this stream to an array.
[use case]Converts this stream to an array.
Note: will not terminate for infinite-sized collections.
- returns
an array containing all elements of this stream. An
ClassTag
must be available for the element type of this stream.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toBuffer[B >: A]: Buffer[B]
Uses the contents of this traversable or iterator to create a new mutable buffer.
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
-
def
toCollection(repr: Stream[A]): collection.LinearSeq[A]
A conversion from collections of type
Repr
to
objects.Seq
A conversion from collections of type
Repr
to
objects. By default this is implemented as just a cast, but this can be overridden.Seq
- Attributes
- protected[this]
- Definition Classes
- LinearSeqLike → SeqLike → IterableLike → TraversableLike
-
def
toIndexedSeq: IndexedSeq[A]
Converts this traversable or iterator to an indexed sequence.
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
-
def
toIterable: collection.Iterable[A]
Returns this iterable collection as an iterable collection.
Returns this iterable collection as an iterable collection.
A new collection will not be built; lazy collections will stay lazy.
Note: will not terminate for infinite-sized collections.
- returns
an
Iterable
containing all elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableOnce → GenTraversableOnce
-
def
toIterator: Iterator[A]
Returns an Iterator over the elements in this iterable collection.
Returns an Iterator over the elements in this iterable collection. Produces the same result as
iterator
.Note: will not terminate for infinite-sized collections.
- returns
an Iterator containing all elements of this iterable collection.
- Definition Classes
- IterableLike → TraversableLike → GenTraversableOnce
- Annotations
- @deprecatedOverriding( message = ... , since = "2.11.0" )
-
def
toList: scala.List[A]
Converts this traversable or iterator to a list.
Converts this traversable or iterator to a list.
Note: will not terminate for infinite-sized collections.
- returns
a list containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toMap[T, U]: collection.Map[T, U]
[use case] Converts this stream to a map.
[use case]Converts this stream 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 stream.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
toParArray: ParArray[T]
- Implicit
- This member is added by an implicit conversion from Stream[A] to CollectionsHaveToParArray[Stream[A], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (Stream[A]) ⇒ GenTraversableOnce[T] is in scope.
- Definition Classes
- CollectionsHaveToParArray
-
def
toSeq: Seq[A]
Converts this immutable sequence to a sequence.
Converts this immutable sequence to a sequence.
Note: will not terminate for infinite-sized collections.
A new collection will not be built; in particular, lazy sequences will stay lazy.
- returns
a sequence containing all elements of this immutable sequence.
- Definition Classes
- Seq → SeqLike → GenSeqLike → TraversableOnce → GenTraversableOnce
-
def
toSet[B >: A]: Set[B]
Converts this traversable or iterator to a set.
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
-
def
toStream: Stream[A]
Converts this stream to a stream.
Converts this stream to a stream.
- returns
a stream containing all elements of this stream.
- Definition Classes
- Stream → IterableLike → TraversableLike → GenTraversableOnce
-
def
toString(): String
Converts this stream to a string.
Converts this stream to a string.
- returns
a string representation of this collection. By default this string consists of the
stringPrefix
of this stream, followed by all elements separated by commas and enclosed in parentheses.
- Definition Classes
- Stream → SeqLike → Function1 → TraversableLike → AnyRef → Any
-
def
toTraversable: collection.Traversable[A]
Converts this traversable collection to an unspecified Traversable.
Converts this traversable collection 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 traversable collection.
- Definition Classes
- TraversableLike → TraversableOnce → GenTraversableOnce
- Annotations
- @deprecatedOverriding( message = ... , since = "2.11.0" )
-
def
toVector: scala.Vector[A]
Converts this traversable or iterator to a Vector.
Converts this traversable or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
- returns
a vector containing all elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
def
transpose[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Stream[Stream[B]]
Transposes this collection of traversable collections into a collection of collections.
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:
val xs = List( Set(1, 2, 3), Set(4, 5, 6)).transpose // xs == List( // List(1, 4), // List(2, 5), // List(3, 6)) val ys = Vector( List(1, 2, 3), List(4, 5, 6)).transpose // ys == Vector( // Vector(1, 4), // Vector(2, 5), // Vector(3, 6))
- 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
.- returns
a two-dimensional collection of collections which has as nth row the nth 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.- Exceptions thrown
IllegalArgumentException
if all collections in this collection are not of the same size.
-
def
union(that: collection.Seq[A]): Stream[A]
[use case] Produces a new sequence which contains all elements of this stream and also all elements of a given sequence.
[use case]Produces a new sequence which contains all elements of this stream and also all elements of a given sequence.
xs union ys
is equivalent toxs ++ ys
.Another way to express this is that
xs union ys
computes the order-preserving multi-set union ofxs
andys
.union
is hence a counter-part ofdiff
andintersect
which also work on multi-sets.Note: will not terminate for infinite-sized collections.
- that
the sequence to add.
- returns
a new stream which contains all elements of this stream followed by all elements of
that
.
- Definition Classes
- SeqLike → GenSeqLike
Full Signaturedef union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
unzip[A1, A2](implicit asPair: (A) ⇒ (A1, A2)): (Stream[A1], Stream[A2])
Converts this collection of pairs into two collections of the first and second half of each pair.
Converts this collection of pairs into two collections of the first and second half of each pair.
val xs = Traversable( (1, "one"), (2, "two"), (3, "three")).unzip // xs == (Traversable(1, 2, 3), // Traversable(one, two, three))
- 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
-
def
unzip3[A1, A2, A3](implicit asTriple: (A) ⇒ (A1, A2, A3)): (Stream[A1], Stream[A2], Stream[A3])
Converts this collection of triples into three collections of the first, second, and third element of each triple.
Converts this collection of triples into three collections of the first, second, and third element of each triple.
val xs = Traversable( (1, "one", '1'), (2, "two", '2'), (3, "three", '3')).unzip3 // xs == (Traversable(1, 2, 3), // Traversable(one, two, three), // Traversable(1, 2, 3))
- 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
-
def
updated(index: Int, elem: A): Stream[A]
[use case] A copy of this stream with one single replaced element.
[use case]A copy of this stream with one single replaced element.
- index
the position of the replacement
- elem
the replacing element
- returns
a copy of this stream with the element at position
index
replaced byelem
.
- Definition Classes
- SeqLike → GenSeqLike
Full Signaturedef updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That
-
def
view: StreamView[A, Stream[A]]
Creates a non-strict view of this stream.
Creates a non-strict view of this stream.
- returns
a non-strict view of this stream.
- Definition Classes
- Stream → SeqLike → IterableLike → TraversableLike
-
def
view(from: Int, until: Int): SeqView[A, Stream[A]]
Creates a non-strict view of a slice of this sequence.
Creates a non-strict view of a slice of this sequence.
Note: the difference between
view
andslice
is thatview
produces a view of the current sequence, whereasslice
produces a new sequence.Note:
view(from, to)
is equivalent toview.slice(from, to)
- from
the index of the first element of the view
- until
the index of the element following the view
- returns
a non-strict view of a slice of this sequence, starting at index
from
and extending up to (but not including) indexuntil
.
- Definition Classes
- SeqLike → IterableLike → TraversableLike
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Stream[A]]
A FilterMonadic which allows GC of the head of stream during processing
A FilterMonadic which allows GC of the head of stream during processing
- 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 stream which satisfy the predicatep
.
- Definition Classes
- Stream → TraversableLike → FilterMonadic
- Annotations
- @noinline()
-
final
def
zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[Stream[A], (A1, B), That]): That
Returns a stream formed from this stream and the specified stream
that
by associating each element of the former with the element at the same position in the latter.Returns a stream formed from this stream and the specified stream
that
by associating each element of the former with the element at the same position in the latter.If one of the two streams is longer than the other, its remaining elements are ignored.
The return type of this function may not be obvious. The lazy aspect of the returned value is different than that of
partition
. Inpartition
we get back a scala.Tuple2 of two lazyStream
s whereas here we get back a single lazyStream
of scala.Tuple2s where the scala.Tuple2's type signature is(A1, B)
.- A1
The type of the first parameter of the zipped tuple
- B
The type of the second parameter of the zipped tuple
- That
The type of the returned
Stream
.- that
The iterable providing the second half of each result pair
- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element type(A1, B)
.- returns
Stream({a0,b0}, ..., {amin(m,n),bmin(m,n))}
whenStream(a0, ..., am) zip Stream(b0, ..., bn)
is invoked.
- Definition Classes
- Stream → IterableLike → GenIterableLike
def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1) naturalsFrom(1) zip naturalsFrom(2) take 5 foreach println // prints // (1,2) // (2,3) // (3,4) // (4,5) // (5,6)
Example: -
def
zipAll[B](that: collection.Iterable[B], thisElem: A, thatElem: B): Stream[(A, B)]
[use case] Returns a stream formed from this stream and another iterable collection by combining corresponding elements in pairs.
[use case]Returns a stream formed from this stream and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
- B
the type of the second half of the returned pairs
- that
The iterable providing the second half of each result pair
- thisElem
the element to be used to fill up the result if this stream is shorter than
that
.- thatElem
the element to be used to fill up the result if
that
is shorter than this stream.- returns
a new stream containing pairs consisting of corresponding elements of this stream and
that
. The length of the returned collection is the maximum of the lengths of this stream andthat
. If this stream is shorter thanthat
,thisElem
values are used to pad the result. Ifthat
is shorter than this stream,thatElem
values are used to pad the result.
- Definition Classes
- IterableLike → GenIterableLike
Full Signaturedef zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Stream[A], (A1, B), That]): That
-
def
zipWithIndex[A1 >: A, That](implicit bf: CanBuildFrom[Stream[A], (A1, Int), That]): That
Zips this iterable with its indices.
Zips this iterable with its indices.
s.zipWithIndex
is equivalent tos zip s.indices
.This method is much like
zip
in that it returns a single lazyStream
of scala.Tuple2.- A1
The type of the first element of the scala.Tuple2 in the resulting stream.
- That
The type of the resulting
Stream
.- bf
an implicit value of class
CanBuildFrom
which determines the result classThat
from the current representation typeRepr
and the new element type(A1, Int)
.- returns
Stream({a0,0}, ..., {an,n)}
- Definition Classes
- Stream → IterableLike → GenIterableLike
def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1) (naturalsFrom(1) zipWithIndex) take 5 foreach println // prints // (1,0) // (2,1) // (3,2) // (4,3) // (5,4)
Example: -
def
→[B](y: B): (Stream[A], B)
- Implicit
- This member is added by an implicit conversion from Stream[A] to ArrowAssoc[Stream[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
Shadowed Implicit Value Members
-
def
filter(p: (A) ⇒ Boolean): TraversableOnce[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(stream: MonadOps[A]).filter(p)
- Definition Classes
- MonadOps
-
def
flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): TraversableOnce[B]
- Implicit
- This member is added by an implicit conversion from Stream[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(stream: MonadOps[A]).flatMap(f)
- Definition Classes
- MonadOps
-
def
map[B](f: (A) ⇒ B): TraversableOnce[B]
- Implicit
- This member is added by an implicit conversion from Stream[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(stream: MonadOps[A]).map(f)
- Definition Classes
- MonadOps
-
def
withFilter(p: (A) ⇒ Boolean): Iterator[A]
- Implicit
- This member is added by an implicit conversion from Stream[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
- Shadowing
- This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:(stream: MonadOps[A]).withFilter(p)
- Definition Classes
- MonadOps
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, including an example implementation of a JSON parser (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
.