Packages

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 a val not a method. The memoization of the Stream requires us to have somewhere to store the information and a val 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 used def to define the Stream) 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, use Iterator 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 of fibs we have an initial (0, 1, Stream(...)) so tail is deterministic. If we defined fibs such that only 0 were concretely known then the act of determining tail would require the evaluation of tail 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.

Linear Supertypes
Known Subclasses
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Stream
  2. Serializable
  3. Serializable
  4. LinearSeqOptimized
  5. LinearSeq
  6. LinearSeq
  7. LinearSeqLike
  8. Seq
  9. Iterable
  10. Traversable
  11. Immutable
  12. AbstractSeq
  13. Seq
  14. SeqLike
  15. GenSeq
  16. GenSeqLike
  17. PartialFunction
  18. Function1
  19. AbstractIterable
  20. Iterable
  21. IterableLike
  22. Equals
  23. GenIterable
  24. GenIterableLike
  25. AbstractTraversable
  26. Traversable
  27. GenTraversable
  28. GenericTraversableTemplate
  29. TraversableLike
  30. GenTraversableLike
  31. Parallelizable
  32. TraversableOnce
  33. GenTraversableOnce
  34. FilterMonadic
  35. HasNewBuilder
  36. AnyRef
  37. Any
Implicitly
  1. by CollectionsHaveToParArray
  2. by MonadOps
  3. by consWrapper
  4. by any2stringadd
  5. by StringFormat
  6. by Ensuring
  7. by ArrowAssoc
  8. by alternateImplicit
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Visibility
  1. Public
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Type Members

  1. 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
  2. type Self = Stream[A]

    The type implementing this traversable

    The type implementing this traversable

    Attributes
    protected[this]
    Definition Classes
    TraversableLike

Abstract Value Members

  1. abstract def tailDefined: Boolean

    Is the tail of this stream defined?

    Is the tail of this stream defined?

    Attributes
    protected

Concrete Value Members

  1. 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
  2. final def ##(): Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. 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. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. def #::[B >: A](hd: B): Stream[B]

    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
  4. def #:::[B >: A](prefix: Stream[B]): Stream[B]

    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
  5. 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
  6. 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 class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[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 class That from the current representation type Repr and the new element type B.

    returns

    A new collection containing the result of concatenating this with that.

    Definition Classes
    StreamTraversableLikeGenTraversableLike
    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 a Stream. For example, referring to the definition of fibs 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 a Stream, or one of its supertypes, or undefined, then StreamBuilder will be chosen for the implicit. We recognize that fact and optimize to get more laziness.

  7. 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, but Traversable and down can use the overload.

    B

    the element type of the returned collection.

    That

    the class of the returned collection. Where possible, That is the same class as the current collection class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.

    that

    the traversable to append.

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    a new collection of type That which contains all elements of this traversable collection followed by all elements of that.

    Definition Classes
    TraversableLike
  8. 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 Signature

    def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  9. 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
    StreamSeqLikeGenSeqLike
    Full Signature

    def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  10. 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()
  11. 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 for foldLeft; z /: xs is the same as xs foldLeft z.

    Examples:

    Note that the folding function used to compute b is equivalent to that used to compute c.

    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 value z 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
    TraversableOnceGenTraversableOnce
  12. 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
    SeqLikeGenSeqLike
    Full Signature

    def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  13. 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 for foldRight; xs :\ z is the same as xs foldRight z.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

    Examples:

    Note that the folding function used to compute b is equivalent to that used to compute c.

    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 value z 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
    TraversableOnceGenTraversableOnce
  14. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (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
  15. 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 string end. Inside, the string representations of defined elements (w.r.t. the method toString()) are separated by the string sep. 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
    StreamTraversableOnce
  16. 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
  17. 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 string sep.

    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
  18. 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 and reduce. It is similar to foldLeft in that it doesn't require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.

    aggregate splits the traversable or iterator into partitions and processes each partition by sequentially applying seqop, starting with z (like foldLeft). Those intermediate results are then combined by using combop (like fold). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), so combop may be invoked an arbitrary number of times (even 0).

    As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First, seqop transforms each input character to an Int and adds it to the sum (of the partition). Then, combop just needs to sum up the intermediate results of the partitions:

    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 or 0 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
    TraversableOnceGenTraversableOnce
  19. 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 to k(this(x)).

    Definition Classes
    PartialFunctionFunction1
  20. 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.

  21. 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, where 0 indicates the first element.

    Definition Classes
    LinearSeqOptimizedSeqLikeGenSeqLike
    Exceptions thrown

    IndexOutOfBoundsException if idx does not satisfy 0 <= idx < length.

  22. 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 to

    if(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 an applyOrElse implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse the basis for the efficient implementation for many operations and scenarios, such as:

    • combining partial functions into orElse/andThen chains does not lead to excessive apply/isDefinedAt evaluation
    • lift and unlift do not evaluate source functions twice on each invocation
    • runWith allows efficient imperative-style combining of partial functions with conditionally applied actions

    For non-literal partial function classes with nontrivial isDefinedAt method it is recommended to override applyOrElse with custom implementation that avoids double isDefinedAt evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.

    x

    the function argument

    default

    the fallback function

    returns

    the result of this function or fallback function application.

    Definition Classes
    PartialFunction
    Since

    2.10

  23. 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 a ClassCastException at runtime, while the expression List(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 type T0.

  24. 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 equal that, false otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.

    Definition Classes
    IterableLikeEquals
  25. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
    Note

    not specified by SLS as a member of AnyRef

  26. 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
    StreamTraversableLikeGenTraversableLike
    Full Signature

    final def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  27. 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
    Example:
    1. Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)

  28. 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
    Example:
    1. "abbbc".combinations(2) = Iterator(ab, ac, bb, bc)

  29. 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 its Iterable superclass where class Stream is not a Seq.)

    Definition Classes
    StreamLinearSeqLinearSeqSeqIterableTraversableSeqGenSeqIterableGenIterableTraversableGenTraversableGenericTraversableTemplate
  30. 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 that f(x) == apply(g(x))

    Definition Classes
    Function1
    Annotations
    @unspecialized()
  31. 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 ==) to elem, false otherwise.

    Definition Classes
    LinearSeqOptimizedSeqLike
  32. 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 as that, otherwise false.

    Definition Classes
    SeqLike
  33. 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 most len elements of this stream, starting at position start. Copying will stop once either the end of the current stream is reached, or the end of the target array is reached, or len elements have been copied.

    Note: will not terminate for infinite-sized collections.

    xs

    the array to fill.

    start

    the starting index.

    len

    the maximal number of elements to copy.

    Definition Classes
    IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit

  34. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: A](xs: Array[B]): Unit

  35. 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 index start. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: A](xs: Array[B], start: Int): Unit

  36. 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
  37. 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 and p(x, y) is true for all corresponding elements x of this sequence and y of that, otherwise false.

    Definition Classes
    LinearSeqLikeSeqLikeGenSeqLike
    Annotations
    @tailrec()
  38. 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
    TraversableOnceGenTraversableOnce
  39. 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 value x appears n times in that, then the first n occurrences of x will not form part of the result, but any following occurrences will.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def diff[B >: A](that: GenSeq[B]): Stream[A]

  40. 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 resulting Stream.

    returns

    A new Stream representing the result of applying distinctness to the original Stream.

    Definition Classes
    StreamSeqLikeGenSeqLike
    Example:
    1. // 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"
  41. 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 than n elements.

    Definition Classes
    StreamLinearSeqOptimizedIterableLikeTraversableLikeGenTraversableLike
    Annotations
    @tailrec()
  42. 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 than n elements.

    Definition Classes
    StreamLinearSeqOptimizedIterableLike
  43. 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 predicate p.

    Returns the a Stream representing the longest suffix of this iterable whose first element does not satisfy the predicate p.

    p

    the test predicate.

    returns

    A new Stream representing the results of applying p to the original Stream.

    Definition Classes
    StreamTraversableLikeGenTraversableLike
    Example:
    1. // 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 predicate p.

  44. 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 has that as a suffix, false otherwise.

    Definition Classes
    SeqLikeGenSeqLike
  45. 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
  46. 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
  47. 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
  48. 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
  49. 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 of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode 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
  50. 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 if that is a sequence that has the same elements as this sequence in the same order, false otherwise

    Definition Classes
    StreamGenSeqLikeEquals → AnyRef → Any
  51. 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, otherwise true if the given predicate p holds for some of the elements of this sequence, otherwise false

    Definition Classes
    LinearSeqOptimizedIterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  52. 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
    TraversableLikeGenTraversableLike
  53. 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
    TraversableLikeGenTraversableLike
  54. 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 between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
    Note

    not specified by SLS as a member of AnyRef

  55. 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, or None if none exists.

    Definition Classes
    LinearSeqOptimizedIterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  56. 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 with map this function does not need to realize the entire Stream but continues to keep it as a lazy Stream.

    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 class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.

    f

    the function to apply on each element.

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    f(a0) ::: ... ::: f(an) if this stream is [a0, ..., an].

    Definition Classes
    StreamTraversableLikeGenTraversableLikeFilterMonadic
    Example:
    1. // 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.

  57. def flatten[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Stream[B]

    Evaluates and concatenates all elements within the Stream into a new flattened Stream.

    Evaluates and concatenates all elements within the Stream into a new flattened Stream.

    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 type B of the flattened elements of this Stream.

    Definition Classes
    StreamGenericTraversableTemplate
    Example:
    1. 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"
  58. 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 and z, or z if this traversable or iterator is empty.

    Definition Classes
    TraversableOnceGenTraversableOnce
  59. 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
    StreamLinearSeqOptimizedTraversableOnceGenTraversableOnce
    Annotations
    @tailrec()
  60. 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 value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))

    where x1, ..., xn are the elements of this sequence. Returns z if this sequence is empty.

    Definition Classes
    LinearSeqOptimizedIterableLikeTraversableOnceGenTraversableOnce
  61. 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 predicate p holds for all elements of this sequence, otherwise false.

    Definition Classes
    LinearSeqOptimizedIterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  62. 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 Streams to represent an infinite set or series. If that's the case for your particular Stream then this function will never return and will probably crash the VM with an OutOfMemory exception. This function will not hang on a finite cycle, however.

  63. 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. Typically U is Unit, but this is not necessary.

    f

    The treatment to apply to each element.

    Definition Classes
    StreamLinearSeqOptimizedIterableLikeGenericTraversableTemplateTraversableLikeGenTraversableLikeTraversableOnceGenTraversableOnceFilterMonadic
    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.

  64. 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 for String.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()
  65. 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
  66. 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
    Annotations
    @native()
  67. 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 elements x for which f(x) equals k.

    Definition Classes
    TraversableLikeGenTraversableLike
  68. 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 size size if the elements don't divide evenly.

    Definition Classes
    IterableLike
    See also

    scala.collection.Iterator, method grouped

  69. 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 returns true if all elements have been computed. It returns false if the stream is not yet evaluated to the end. Non-empty Iterators usually return false 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 returns true. However, checking hasDefiniteSize 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
    StreamTraversableLikeTraversableOnceGenTraversableOnce
  70. 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
    LinearSeqLikeGenSeqLike → AnyRef → Any
  71. 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
    IterableLikeTraversableLikeGenTraversableLike
    Exceptions thrown

    NoSuchElementException if the iterable collection is empty.

  72. 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
    TraversableLikeGenTraversableLike
  73. 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 ==) to elem, or -1, if none exists.

    Definition Classes
    GenSeqLike
    Full Signature

    def indexOf[B >: A](elem: B, from: Int): Int

  74. 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 ==) to elem, or -1, if none exists.

    Definition Classes
    GenSeqLike
    Full Signature

    def indexOf[B >: A](elem: B): Int

  75. 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 sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqLike
  76. 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
  77. 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 predicate p, or -1, if none exists.

    Definition Classes
    LinearSeqOptimizedSeqLikeGenSeqLike
  78. 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
  79. 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 from 0 to one less than the length of this sequence.

    Definition Classes
    SeqLike
  80. 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 your Stream represents an infinite series, this method will not return.

    Definition Classes
    StreamTraversableLikeGenTraversableLike
    Exceptions thrown

    UnsupportedOperationException if the stream is empty.

  81. 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
    Example:
    1. List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)

  82. 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 value x appears n times in that, then the first n occurrences of x will be retained in the result, but any following occurrences will be omitted.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def intersect[B >: A](that: GenSeq[B]): Stream[A]

  83. def isDefinedAt(x: Int): Boolean

    Tests whether this sequence contains given index.

    Tests whether this sequence contains given index.

    The implementations of methods apply and isDefinedAt turn a Seq[A] into a PartialFunction[Int, A].

    returns

    true if this sequence contains an element at position idx, false otherwise.

    Definition Classes
    LinearSeqOptimizedGenSeqLike
  84. 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
    SeqLikeIterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  85. 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 return false, while the expression List(1).isInstanceOf[List[String]] will return true. 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 type T0; false otherwise.

    Definition Classes
    Any
  86. 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
    TraversableLikeGenTraversableLikeGenTraversableOnce
  87. def iterator: Iterator[A]

    A lazier Iterator than LinearSeqLike's.

    A lazier Iterator than LinearSeqLike's.

    returns

    the new iterator

    Definition Classes
    StreamLinearSeqLikeIterableLikeGenIterableLike
  88. def last: A

    Selects the last element.

    Selects the last element.

    returns

    The last element of this sequence.

    Definition Classes
    LinearSeqOptimizedTraversableLikeGenTraversableLike
    Exceptions thrown

    NoSuchElementException If the sequence is empty.

  89. 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 ==) to elem, or -1, if none exists.

    Definition Classes
    GenSeqLike
    Full Signature

    def lastIndexOf[B >: A](elem: B, end: Int): Int

  90. 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 ==) to elem, or -1, if none exists.

    Definition Classes
    GenSeqLike
    Full Signature

    def lastIndexOf[B >: A](elem: B): Int

  91. 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 sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqLike
  92. 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
  93. 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 predicate p, or -1, if none exists.

    Definition Classes
    LinearSeqOptimizedSeqLikeGenSeqLike
  94. 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
  95. 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
    TraversableLikeGenTraversableLike
  96. def length: Int

    Returns the length of this Stream.

    Returns the length of this Stream.

    returns

    The length of this Stream.

    Definition Classes
    StreamLinearSeqOptimizedSeqLikeGenSeqLike
    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 your Stream represents.

  97. 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 where

    x <  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 is O(length min len) instead of O(length). The method should be overwritten if computing length is cheap.

    Definition Classes
    LinearSeqOptimizedSeqLike
  98. 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 to Some(this(x)) if this is defined for x, and to None otherwise.

    Definition Classes
    PartialFunction
    See also

    Function.unlift

  99. 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 lazy Stream 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 class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.

    f

    function to apply to each element.

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    f(a0), ..., f(an) if this sequence is a0, ..., an.

    Definition Classes
    StreamTraversableLikeGenTraversableLikeFilterMonadic
    Example:
    1. def naturalsFrom(i: Int): Stream[Int] = i #:: naturalsFrom(i + 1)
      naturalsFrom(1).map(_ + 10) take 5 mkString(", ")
      // produces: "11, 12, 13, 14, 15"
  100. def max: A

    [use case] Finds the largest element.

    [use case]

    Finds the largest element.

    returns

    the largest element of this stream.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def max[B >: A](implicit cmp: Ordering[B]): A

  101. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

  102. def min: A

    [use case] Finds the smallest element.

    [use case]

    Finds the smallest element.

    returns

    the smallest element of this stream

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def min[B >: A](implicit cmp: Ordering[B]): A

  103. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

  104. 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 string end. Inside, the string representations (w.r.t. the method toString) of all elements of this stream are separated by the string sep.

    Definition Classes
    StreamTraversableOnceGenTraversableOnce
    Example:
    1. List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

  105. 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
    StreamTraversableOnceGenTraversableOnce
  106. 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 string sep.

    Definition Classes
    StreamTraversableOnceGenTraversableOnce
    Example:
    1. List(1, 2, 3).mkString("|") = "1|2|3"

  107. 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
  108. 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
    GenericTraversableTemplateHasNewBuilder
  109. 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
    TraversableOnceGenTraversableOnce
  110. 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
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  111. 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
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  112. 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 takes x to this(x) where this is defined, and to that(x) where it is not.

    Definition Classes
    PartialFunction
  113. 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 class That from the current representation type Repr and the new element type B.

    returns

    A new Stream representing the collection with values padding off to the end. If your Stream represents an infinite series, this method will not return.

    Definition Classes
    StreamSeqLikeGenSeqLike
    Example:
    1. 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
  114. 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 or mutable.ParHashMap) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

    All parallel collections return a reference to themselves.

    returns

    a parallel implementation of this collection

    Definition Classes
    Parallelizable
  115. 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
    SeqSeqLikeIterableTraversableLikeParallelizable
  116. 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 of Streams obeying the partition predicate p.

    Returns all the elements of this stream that satisfy the predicate p returning of scala.Tuple2 of Streams obeying the partition predicate p. 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
    StreamTraversableLikeGenTraversableLike
    Example:
    1. 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"
  117. 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 from from are replaced by patch.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  118. 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
    Example:
    1. "abb".permutations = Iterator(abb, bab, bba)

  119. 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
  120. 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.

  121. def print(): Unit

    Prints elements of this stream one by one, separated by commas.

  122. 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 of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the stream and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def product[B >: A](implicit num: Numeric[B]): B

  123. 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
    TraversableOnceGenTraversableOnce
    Exceptions thrown

    UnsupportedOperationException if this traversable or iterator is empty.

  124. 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
    StreamLinearSeqOptimizedTraversableOnce
  125. 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
    TraversableOnceGenTraversableOnce
  126. 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, and None otherwise.

    Definition Classes
    TraversableOnceGenTraversableOnce
  127. 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
    LinearSeqOptimizedIterableLikeTraversableOnceGenTraversableOnce
    Exceptions thrown

    UnsupportedOperationException if this sequence is empty.

  128. 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
    TraversableOnceGenTraversableOnce
  129. 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 the TraversableLike object itself, but this can be overridden.

    Definition Classes
    TraversableLikeGenTraversableLike
  130. 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 original Stream in reverse order.

    Definition Classes
    StreamSeqLikeGenSeqLike
    Example:
    1. 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 your Stream represents an infinite sequence then this function will never return.

  131. 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 as xs.reverse.iterator but might be more efficient.

    returns

    an iterator yielding the elements of this sequence in reversed order

    Definition Classes
    SeqLike
  132. 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 as xs.reverse.map(f) but might be more efficient.

    B

    the element type of the returned collection.

    f

    the function to apply to each element.

    returns

    a new stream resulting from applying the given function f to each element of this stream and collecting the results in reversed order.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def reverseMap[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  133. def reversed: scala.List[A]
    Attributes
    protected[this]
    Definition Classes
    TraversableOnce
  134. 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 to

    if(pf isDefinedAt x) { action(pf(x)); true } else false

    except that runWith is implemented via applyOrElse and thus potentially more efficient. Using runWith avoids double evaluation of pattern matchers and guards for partial function literals.

    action

    the action function

    returns

    a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.

    Definition Classes
    PartialFunction
    Since

    2.10

    See also

    applyOrElse.

  135. 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
    LinearSeqOptimizedIterableLikeGenIterableLike
    Full Signature

    def sameElements[B >: A](that: GenIterable[B]): Boolean

  136. 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
    TraversableLikeGenTraversableLike
  137. 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 to foldLeft.

    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 class That from the current representation type Repr and the new element type B.

    returns

    A new collection containing the modifications from the application of op.

    Definition Classes
    StreamTraversableLikeGenTraversableLike
    Note

    This works because the target type of the scala.collection.mutable.Builder That is a Stream.

  138. 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 class That from the current representation type Repr and the new element type B.

    returns

    collection with intermediate results

    Definition Classes
    TraversableLikeGenTraversableLike
    Annotations
    @migration
    Migration

    (Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.

  139. 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 predicate p.

    Definition Classes
    LinearSeqOptimizedSeqLikeGenSeqLike
  140. 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
    LinearSeqLinearSeqLinearSeqLikeSeqSeqGenSeqGenSeqLikeIterableIterableGenIterableTraversableTraversableGenTraversableParallelizableTraversableOnceGenTraversableOnce
  141. 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
    SeqLikeGenTraversableLikeTraversableOnceGenTraversableOnce
  142. 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
  143. def slice(from: Int, until: Int): Stream[A]

    A substream starting at index from and extending up to (but not including) index until.

    A substream starting at index from and extending up to (but not including) index until. This returns a Stream 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 until end.

    Definition Classes
    StreamLinearSeqOptimizedIterableLikeTraversableLikeGenTraversableLike
    Example:
    1. naturalsFrom(0) slice(50, 60) mkString ", "
      // produces: "50, 51, 52, 53, 54, 55, 56, 57, 58, 59"
  144. 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 element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.

    Definition Classes
    IterableLike
    See also

    scala.collection.Iterator, method sliding

  145. 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.) The "sliding window" step is set to one.

    Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) The "sliding window" step is set to one.

    size

    the number of elements per group

    returns

    An iterator producing iterable collections of size size, except the last element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.

    Definition Classes
    IterableLike
    See also

    scala.collection.Iterator, method sliding

  146. 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 ordering ord 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 if ord.lt(f(x), f(y)).

    Definition Classes
    SeqLike
    Example:
    1. 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.

  147. 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
    Example:
    1. List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
      List("Bob", "John", "Steve", "Tom")
  148. 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

    scala.math.Ordering

  149. 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 predicate p 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
    LinearSeqOptimizedTraversableLikeGenTraversableLike
  150. 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
    StreamTraversableLikeGenTraversableLike
  151. 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 argument that are infinite sequences this method may not terminate.

    that

    the sequence to test

    offset

    the index where the sequence is searched.

    returns

    true if the sequence that is contained in this sequence at index offset, otherwise false.

    Definition Classes
    SeqLikeGenSeqLike
  152. 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 has that as a prefix, false otherwise.

    Definition Classes
    GenSeqLike
  153. def stringPrefix: String

    Defines the prefix of this object's toString representation as Stream.

    Defines the prefix of this object's toString representation as Stream.

    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
    StreamTraversableLikeGenTraversableLike
  154. 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 of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the stream and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def sum[B >: A](implicit num: Numeric[B]): B

  155. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  156. 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
    TraversableLikeGenTraversableLike
    Exceptions thrown

    `UnsupportedOperationException` if the traversable collection is empty.

  157. 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
    Example:
    1. List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)

  158. def take(n: Int): Stream[A]

    Returns the n first elements of this Stream as another Stream, or else the whole Stream, if it has less than n elements.

    Returns the n first elements of this Stream as another Stream, or else the whole Stream, if it has less than n elements.

    The result of take is, again, a Stream meaning that it also does not make any needless evaluations of the Stream itself, delaying that until the usage of the resulting Stream.

    n

    the number of elements to take.

    returns

    the n first elements of this stream.

    Definition Classes
    StreamLinearSeqOptimizedIterableLikeTraversableLikeGenTraversableLike
    Example:
    1. 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"
  159. 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 this Stream.

    Definition Classes
    StreamIterableLike
    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.

  160. def takeWhile(p: (A) ⇒ Boolean): Stream[A]

    Returns the longest prefix of this Stream whose elements satisfy the predicate p.

    Returns the longest prefix of this Stream whose elements satisfy the predicate p.

    p

    the test predicate.

    returns

    A new Stream representing the values that satisfy the predicate p.

    Definition Classes
    StreamLinearSeqOptimizedIterableLikeTraversableLikeGenTraversableLike
    Example:
    1.    + naturalsFrom(0) takeWhile { _ < 5 } mkString ", "
      produces: "0, 1, 2, 3, 4"
  161. def thisCollection: collection.LinearSeq[A]

    The underlying collection seen as an instance of Seq.

    The underlying collection seen as an instance of Seq. By default this is implemented as the current collection object itself, but this can be overridden.

    Attributes
    protected[this]
    Definition Classes
    LinearSeqLikeSeqLikeIterableLikeTraversableLike
  162. 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
    TraversableLikeTraversableOnceGenTraversableOnce
    Full Signature

    def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]

  163. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]

  164. 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
    TraversableOnceGenTraversableOnce
  165. def toCollection(repr: Stream[A]): collection.LinearSeq[A]

    A conversion from collections of type Repr to Seq objects.

    A conversion from collections of type Repr to Seq objects. By default this is implemented as just a cast, but this can be overridden.

    Attributes
    protected[this]
    Definition Classes
    LinearSeqLikeSeqLikeIterableLikeTraversableLike
  166. 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
    TraversableOnceGenTraversableOnce
  167. 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
    IterableLikeTraversableOnceGenTraversableOnce
  168. 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
    IterableLikeTraversableLikeGenTraversableOnce
    Annotations
    @deprecatedOverriding( message = ... , since = "2.11.0" )
  169. 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
    TraversableOnceGenTraversableOnce
  170. 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
    TraversableOnceGenTraversableOnce
    Full Signature

    def toMap[T, U](implicit ev: <:<[A, (T, U)]): Map[T, U]

  171. 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
  172. 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
    SeqSeqLikeGenSeqLikeTraversableOnceGenTraversableOnce
  173. 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
    TraversableOnceGenTraversableOnce
  174. 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
    StreamIterableLikeTraversableLikeGenTraversableOnce
  175. 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
    StreamSeqLikeFunction1TraversableLike → AnyRef → Any
  176. 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
    TraversableLikeTraversableOnceGenTraversableOnce
    Annotations
    @deprecatedOverriding( message = ... , since = "2.11.0" )
  177. 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
    TraversableOnceGenTraversableOnce
  178. 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 an IllegalArgumentException if collections are not uniformly sized.

    Exceptions thrown

    IllegalArgumentException if all collections in this collection are not of the same size.

  179. 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 to xs ++ ys.

    Another way to express this is that xs union ys computes the order-preserving multi-set union of xs and ys. union is hence a counter-part of diff and intersect which also work on multi-sets.

    Note: will not terminate for infinite-sized collections.

    that

    the sequence to add.

    returns

    a new stream which contains all elements of this stream followed by all elements of that.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  180. 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
  181. 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
  182. 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 by elem.

    Definition Classes
    SeqLikeGenSeqLike
    Full Signature

    def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Stream[A], B, That]): That

  183. 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
    StreamSeqLikeIterableLikeTraversableLike
  184. 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 and slice is that view produces a view of the current sequence, whereas slice produces a new sequence.

    Note: view(from, to) is equivalent to view.slice(from, to)

    from

    the index of the first element of the view

    until

    the index of the element following the view

    returns

    a non-strict view of a slice of this sequence, starting at index from and extending up to (but not including) index until.

    Definition Classes
    SeqLikeIterableLikeTraversableLike
  185. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  186. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  187. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  188. 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 supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this stream which satisfy the predicate p.

    Definition Classes
    StreamTraversableLikeFilterMonadic
    Annotations
    @noinline()
  189. 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. In partition we get back a scala.Tuple2 of two lazy Streams whereas here we get back a single lazy Stream 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 class That from the current representation type Repr and the new element type (A1, B).

    returns

    Stream({a0,b0}, ..., {amin(m,n),bmin(m,n))} when Stream(a0, ..., am) zip Stream(b0, ..., bn) is invoked.

    Definition Classes
    StreamIterableLikeGenIterableLike
    Example:
    1. 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)
  190. 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 and that. If this stream is shorter than that, thisElem values are used to pad the result. If that is shorter than this stream, thatElem values are used to pad the result.

    Definition Classes
    IterableLikeGenIterableLike
    Full Signature

    def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Stream[A], (A1, B), That]): That

  191. 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 to s zip s.indices.

    This method is much like zip in that it returns a single lazy Stream 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 class That from the current representation type Repr and the new element type (A1, Int).

    returns

    Stream({a0,0}, ..., {an,n)}

    Definition Classes
    StreamIterableLikeGenIterableLike
    Example:
    1. 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)
  192. 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

  1. 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
  2. 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
  3. 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
  4. 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

Inherited from Serializable

Inherited from java.io.Serializable

Inherited from LinearSeqOptimized[A, Stream[A]]

Inherited from LinearSeq[A]

Inherited from collection.LinearSeq[A]

Inherited from LinearSeqLike[A, Stream[A]]

Inherited from Seq[A]

Inherited from Iterable[A]

Inherited from Traversable[A]

Inherited from Immutable

Inherited from AbstractSeq[A]

Inherited from collection.Seq[A]

Inherited from SeqLike[A, Stream[A]]

Inherited from GenSeq[A]

Inherited from GenSeqLike[A, Stream[A]]

Inherited from PartialFunction[Int, A]

Inherited from (Int) ⇒ A

Inherited from AbstractIterable[A]

Inherited from collection.Iterable[A]

Inherited from IterableLike[A, Stream[A]]

Inherited from Equals

Inherited from GenIterable[A]

Inherited from GenIterableLike[A, Stream[A]]

Inherited from AbstractTraversable[A]

Inherited from collection.Traversable[A]

Inherited from GenTraversable[A]

Inherited from GenericTraversableTemplate[A, Stream]

Inherited from TraversableLike[A, Stream[A]]

Inherited from GenTraversableLike[A, Stream[A]]

Inherited from Parallelizable[A, ParSeq[A]]

Inherited from TraversableOnce[A]

Inherited from GenTraversableOnce[A]

Inherited from FilterMonadic[A, Stream[A]]

Inherited from HasNewBuilder[A, scala.collection.immutable.Stream[A] @scala.annotation.unchecked.uncheckedVariance]

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion CollectionsHaveToParArray from Stream[A] to CollectionsHaveToParArray[Stream[A], T]

Inherited by implicit conversion MonadOps from Stream[A] to MonadOps[A]

Inherited by implicit conversion consWrapper from Stream[A] to ConsWrapper[A]

Inherited by implicit conversion any2stringadd from Stream[A] to any2stringadd[Stream[A]]

Inherited by implicit conversion StringFormat from Stream[A] to StringFormat[Stream[A]]

Inherited by implicit conversion Ensuring from Stream[A] to Ensuring[Stream[A]]

Inherited by implicit conversion ArrowAssoc from Stream[A] to ArrowAssoc[Stream[A]]

Inherited by implicit conversion alternateImplicit from Stream[A] to ForceImplicitAmbiguity

Ungrouped