in scala
trait Stream

abstract trait Stream [a]
extends java.lang.Object
with scala.Seq[a]
with scala.ScalaObject

The class Stream implements lazy lists where elements are only evaluated when they are needed. Here is an example:

 object Main extends Application {

   def from(n: Int): Stream[Int] =
     Stream.cons(n, from(n + 1))

   def sieve(s: Stream[Int]): Stream[Int] =
     Stream.cons(s.head, sieve(s.tail filter { x => x % s.head != 0 }))

   def primes = sieve(from(2))

   primes take 10 print
 }
 
Author:
Martin Odersky, Matthias Zenger
Version:
1.1 08/08/03

Def Summary
abstract protected def addDefinedElems (buf: scala.compat.StringBuilder, prefix: java.lang.String) : scala.compat.StringBuilder
Write all elements of this string into given string builder
def append [b >: a] (rest: => scala.Stream[b]) : scala.Stream[b]
The stream resulting from the concatenation of thsi stream with the argument stream.
def apply (n: scala.Int) : a
Returns the n-th element of this stream. The first element (head of the stream) is at position 0.
override def copyToArray [b >: a] (xs: scala.Array[b], start: scala.Int) : scala.Unit
Fills the given array xs with the elements of this stream starting at position start.
override def drop (n: scala.Int) : scala.Stream[a]
Returns the stream without its n first elements. If the stream has less than n elements, the empty stream is returned.
override def dropWhile (p: (a) => scala.Boolean) : scala.Stream[a]
Returns the longest suffix of this stream whose first element does not satisfy the predicate p.
def elements : scala.Iterator[a]
An iterator returning the elements of this stream one by one.
override def exists (p: (a) => scala.Boolean) : scala.Boolean
Tests the existence in this stream of an element that satisfies the predicate p.
override def filter (p: (a) => scala.Boolean) : scala.Stream[a]
Returns all the elements of this stream that satisfy the predicate p. The order of the elements is preserved.
override def flatMap [b] (f: (a) => scala.Iterable[b]) : scala.Stream[b]
Applies the given function f to each element of this stream, then concatenates the results.
override def foldLeft [b] (z: b)(f: (b, a) => b) : b
Combines the elements of this stream together using the binary function f, from left to right, and starting with the value z.
override def foldRight [b] (z: b)(f: (a, b) => b) : b
Combines the elements of this stream together using the binary function f, from rigth to left, and starting with the value z.
override def forall (p: (a) => scala.Boolean) : scala.Boolean
Tests if the predicate p is satisfied by all elements in this stream.
override def foreach (f: (a) => scala.Unit) : scala.Unit
Apply the given function f to each element of this stream (while respecting the order of the elements).
abstract def head : a
The first element of this stream
def init : scala.Stream[a]
The stream without its last element.
abstract override def isEmpty : scala.Boolean
is this stream empty?
def last : a
Returns the last element of this stream.
def length : scala.Int
The length of this stream
override def map [b] (f: (a) => b) : scala.Stream[b]
Returns the stream resulting from applying the given function f to each element of this stream.
def print (out: java.io.PrintStream) : scala.Unit

def print (out: java.io.PrintStream, sep: java.lang.String) : scala.Unit

def print (sep: java.lang.String) : scala.Unit
Prints elements of this stream one by one, separated by sep
def print : scala.Unit
Prints elements of this stream one by one, separated by commas
override def reverse : scala.Stream[a]
A stream consisting of all elements of this stream in reverse order.
abstract def tail : scala.Stream[a]
A stream consisting of the remaining elements of this stream after the first one.
override def take (n: scala.Int) : scala.Stream[a]
Returns the n first elements of this stream, or else the whole stream, if it has less than n elements.
override def takeWhile (p: (a) => scala.Boolean) : scala.Stream[a]
Returns the longest prefix of this stream whose elements satisfy the predicate p.
override def toString : java.lang.String
Converts stream to string
def zip [b] (that: scala.Stream[b]) : scala.Stream[scala.Tuple2[a, b]]
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.
def zipWithIndex : scala.Stream[scala.Tuple2[a, scala.Int]]
Returns a stream that pairs each element of this stream with its index, counting from 0.
Def inherited from scala.Seq[a]
++ , concat, contains, copyToArray, drop, dropWhile, filter, flatMap, isDefinedAt, isEmpty, lastIndexOf, length, map, reverse, slice, stringPrefix, subseq, super$drop, super$dropWhile, super$filter, super$take, super$takeWhile, take, takeWhile, toArray, toString
Def Detail
abstract protected def addDefinedElems (buf: scala.compat.StringBuilder, prefix: java.lang.String): scala.compat.StringBuilder
Write all elements of this string into given string builder

def append [b >: a](rest: => scala.Stream[b]): scala.Stream[b]
The stream resulting from the concatenation of thsi stream with the argument stream.
Parameters:
rest - The stream that gets appended to this stream

def apply (n: scala.Int): a
Returns the n-th element of this stream. The first element (head of the stream) is at position 0.
Parameters:
n - index of the element to return
Returns:
the element at position n in this stream.
Throws:
Predef.NoSuchElementException - if the stream is too short.

override def copyToArray [b >: a](xs: scala.Array[b], start: scala.Int): scala.Unit
Fills the given array xs with the elements of this stream starting at position start.
Parameters:
xs - the array to fill.
Parameters:
start - starting index.
Precondition:
the array must be large enough to hold all elements.

override def drop (n: scala.Int): scala.Stream[a]
Returns the stream without its n first elements. If the stream has less than n elements, the empty stream is returned.
Parameters:
n - the number of elements to drop.
Returns:
the stream without its n first elements.

override def dropWhile (p: (a) => scala.Boolean): scala.Stream[a]
Returns the longest suffix of this stream whose first element does not satisfy the predicate p.
Parameters:
p - the test predicate.
Returns:
the longest suffix of the stream whose first element does not satisfy the predicate p.

def elements : scala.Iterator[a]
An iterator returning the elements of this stream one by one.

override def exists (p: (a) => scala.Boolean): scala.Boolean
Tests the existence in this stream of an element that satisfies the predicate p.
Parameters:
p - the test predicate.
Returns:
true iff there exists an element in this stream that satisfies the predicate p.

override def filter (p: (a) => scala.Boolean): scala.Stream[a]
Returns all the elements of this stream that satisfy the predicate p. The order of the elements is preserved.
Parameters:
p - the predicate used to filter the stream.
Returns:
the elements of this stream satisfying p.

override def flatMap [b](f: (a) => scala.Iterable[b]): scala.Stream[b]
Applies the given function f to each element of this stream, then concatenates the results.
Parameters:
f - the function to apply on each element.
Returns:
f(a0) ::: ... ::: f(an) if this stream is [a0, ..., an].

override def foldLeft [b](z: b)(f: (b, a) => b): b
Combines the elements of this stream together using the binary function f, from left to right, and starting with the value z.
Returns:
f(... (f(f(z, a0), a1) ...), an) if the stream is [a0, a1, ..., an].

override def foldRight [b](z: b)(f: (a, b) => b): b
Combines the elements of this stream together using the binary function f, from rigth to left, and starting with the value z.
Returns:
f(a0, f(a1, f(..., f(an, z)...))) if the stream is [a0, a1, ..., an].

override def forall (p: (a) => scala.Boolean): scala.Boolean
Tests if the predicate p is satisfied by all elements in this stream.
Parameters:
p - the test predicate.
Returns:
true iff all elements of this stream satisfy the predicate p.

override def foreach (f: (a) => scala.Unit): scala.Unit
Apply the given function f to each element of this stream (while respecting the order of the elements).
Parameters:
f - the treatment to apply to each element.

abstract def head : a
The first element of this stream
Throws:
Predef.NoSuchElementException - if the stream is empty.

def init : scala.Stream[a]
The stream without its last element.
Throws:
Predef.UnsupportedOperationException - if the stream is empty.

abstract override def isEmpty : scala.Boolean
is this stream empty?

def last : a
Returns the last element of this stream.
Returns:
the last element of the stream.
Throws:
Predef.NoSuchElementException - if the stream is empty.

def length : scala.Int
The length of this stream

override def map [b](f: (a) => b): scala.Stream[b]
Returns the stream resulting from applying the given function f to each element of this stream.
Parameters:
f - function to apply to each element.
Returns:
[f(a0), ..., f(an)] if this stream is [a0, ..., an].

def print (out: java.io.PrintStream): scala.Unit

def print (out: java.io.PrintStream, sep: java.lang.String): scala.Unit

def print (sep: java.lang.String): scala.Unit
Prints elements of this stream one by one, separated by sep
Parameters:
sep - The separator string printed between consecutive elements.

def print : scala.Unit
Prints elements of this stream one by one, separated by commas

override def reverse : scala.Stream[a]
A stream consisting of all elements of this stream in reverse order.

abstract def tail : scala.Stream[a]
A stream consisting of the remaining elements of this stream after the first one.
Throws:
Predef.UnsupportedOperationException - if the stream is empty.

override def take (n: scala.Int): scala.Stream[a]
Returns the n first elements of this stream, or else the whole stream, if it has less than n elements.
Parameters:
n - the number of elements to take.
Returns:
the n first elements of this stream.

override def takeWhile (p: (a) => scala.Boolean): scala.Stream[a]
Returns the longest prefix of this stream whose elements satisfy the predicate p.
Parameters:
p - the test predicate.
Returns:
the longest prefix of this stream whose elements satisfy the predicate p.

override def toString : java.lang.String
Converts stream to string

def zip [b](that: scala.Stream[b]): scala.Stream[scala.Tuple2[a, b]]
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.
Returns:
Stream({a0,b0}, ..., {amin(m,n),bmin(m,n))} when Stream(a0, ..., am) zip Stream(b0, ..., bn) is invoked.

def zipWithIndex : scala.Stream[scala.Tuple2[a, scala.Int]]
Returns a stream that pairs each element of this stream with its index, counting from 0.
Returns:
the stream Stream({a0,0}, {a0,1},...) where ai are the elements of this stream.