scala

trait Stream

[source: scala/Stream.scala]

trait Stream[+A]
extends Projection[A]

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 { _ % s.head != 0 }))

   def primes = sieve(from(2))

   primes take 10 print
 }
 
Author
Martin Odersky, Matthias Zenger
Version
1.1 08/08/03
Direct Known Subclasses:
Stream.Definite

Method Summary
protected abstract def addDefinedElems (buf : StringBuilder, prefix : String) : StringBuilder
Write all elements of this string into given string builder
override def append [B >: A](rest : => Iterable[B]) : Stream[B]
The stream resulting from the concatenation of this stream with the argument stream.
override def apply (n : 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 : Array[B], start : Int) : Unit
Fills the given array xs with the elements of this stream starting at position start.
override def drop (n : Int) : 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) => Boolean) : Stream[A]
Returns the longest suffix of this stream whose first element does not satisfy the predicate p.
override def elements : Iterator[A]
An iterator returning the elements of this stream one by one.
override def exists (p : (A) => Boolean) : Boolean
Tests the existence in this stream of an element that satisfies the predicate p.
override def filter (p : (A) => Boolean) : 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) => Iterable[B]) : 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) => Boolean) : Boolean
Tests if the predicate p is satisfied by all elements in this stream.
override def force : List[A]
convert to a copied strict collection
override def foreach (f : (A) => Unit) : Unit
Apply the given function f to each element of this stream (while respecting the order of the elements).
override def hasDefiniteSize : Boolean
returns true iff this collection has a bound size. Many APIs in this trait will not work on collections of unbound sizes.
abstract def head : A
The first element of this stream
def init : Stream[A]
The stream without its last element.
override abstract def isEmpty : Boolean
is this stream empty?
override def last : A
Returns the last element of this stream.
override def length : Int
The length of this stream
override def map [B](f : (A) => B) : Stream[B]
Returns the stream resulting from applying the given function f to each element of this stream.
def print : Unit
Prints elements of this stream one by one, separated by commas
def print (sep : String) : Unit
Prints elements of this stream one by one, separated by sep
override def reverse : Stream[A]
A stream consisting of all elements of this stream in reverse order.
abstract def tail : Stream[A]
A stream consisting of the remaining elements of this stream after the first one.
override def take (n : Int) : 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) => Boolean) : Stream[A]
Returns the longest prefix of this stream whose elements satisfy the predicate p.
override def toStream : Stream[A]
Create a stream which contains all the elements of this iterable object.
override def toString : String
Converts stream to string
def zip [B](that : Stream[B]) : Stream[(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 : Stream[(A, Int)]
Returns a stream that pairs each element of this stream with its index, counting from 0.
Methods inherited from Projection
projection
Methods inherited from Seq
size, concat, lastOption, headOption, ++, isDefinedAt, lastIndexOf, slice, contains, subseq, toArray, equalsWith, startsWith, endsWith, indexOf, containsSlice
Methods inherited from Collection
stringPrefix
Methods inherited from Iterable
find, findIndexOf, indexOf, /:, :\, reduceLeft, reduceRight, copyToBuffer, sameElements, toList, mkString, mkString, mkString, addString, addString
Methods inherited from PartialFunction
orElse, andThen
Methods inherited from Function1
compose
Methods inherited from AnyRef
getClass, hashCode, equals, clone, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized
Methods inherited from Any
==, !=, isInstanceOf, asInstanceOf