scala.collection.mutable.Queue

object Queue extends SeqFactory[Queue] with Serializable

Type Members

type Coll = Queue[_]

The underlying collection type with unknown element type

  • Attributes
    • protected[this]
  • Definition Classes
    • GenericCompanion

class GenericCanBuildFrom[A] extends CanBuildFrom[CC[_], A, CC[A]]

A generic implementation of the CanBuildFrom trait, which forwards all calls to apply(from) to the genericBuilder method of collection from , and which forwards all calls of apply() to the newBuilder method of this factory.

  • Definition Classes
    • GenTraversableFactory

Value Members From scala.collection.generic.GenTraversableFactory

def ReusableCBF: GenericCanBuildFrom[Nothing]

  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def concat[A](xss: collection.Traversable[A]*): Queue[A]

Concatenates all argument collections into a single collection.

  • xss
    • the collections that are to be concatenated.
  • returns
    • the concatenation of all the collections.
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def fill[A](n: Int)(elem: ⇒ A): Queue[A]

Produces a collection containing the results of some element computation a number of times.

  • n
    • the number of elements contained in the collection.
  • elem
    • the element computation
  • returns
    • A collection that contains the results of n evaluations of elem .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def fill[A](n1: Int, n2: Int)(elem: ⇒ A): Queue[Queue[A]]

Produces a two-dimensional collection containing the results of some element computation a number of times.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • elem
    • the element computation
  • returns
    • A collection that contains the results of n1 x n2 evaluations of elem .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def fill[A](n1: Int, n2: Int, n3: Int)(elem: ⇒ A): Queue[Queue[Queue[A]]]

Produces a three-dimensional collection containing the results of some element computation a number of times.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • elem
    • the element computation
  • returns
    • A collection that contains the results of n1 x n2 x n3 evaluations of elem .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def fill[A](n1: Int, n2: Int, n3: Int, n4: Int)(elem: ⇒ A): Queue[Queue[Queue[Queue[A]]]]

Produces a four-dimensional collection containing the results of some element computation a number of times.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • n4
    • the number of elements in the 4th dimension
  • elem
    • the element computation
  • returns
    • A collection that contains the results of n1 x n2 x n3 x n4 evaluations of elem .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def fill[A](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int)(elem: ⇒ A): Queue[Queue[Queue[Queue[Queue[A]]]]]

Produces a five-dimensional collection containing the results of some element computation a number of times.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • n4
    • the number of elements in the 4th dimension
  • n5
    • the number of elements in the 5th dimension
  • elem
    • the element computation
  • returns
    • A collection that contains the results of n1 x n2 x n3 x n4 x n5 evaluations of elem .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def iterate[A](start: A, len: Int)(f: (A) ⇒ A): Queue[A]

Produces a collection containing repeated applications of a function to a start value.

  • start
    • the start value of the collection
  • len
    • the number of elements contained inthe collection
  • f
    • the function that’s repeatedly applied
  • returns
    • a collection with len values in the sequence start, f(start), f(f(start)), ...
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def range[T](start: T, end: T)(implicit arg0: Integral[T]): Queue[T]

Produces a collection containing a sequence of increasing of integers.

  • start
    • the first element of the collection
  • end
    • the end value of the collection (the first value NOT contained)
  • returns
    • a collection with values start, start + 1, ..., end - 1
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def range[T](start: T, end: T, step: T)(implicit arg0: Integral[T]): Queue[T]

Produces a collection containing equally spaced values in some integer interval.

  • start
    • the start value of the collection
  • end
    • the end value of the collection (the first value NOT contained)
  • step
    • the difference between successive elements of the collection (must be positive or negative)
  • returns
    • a collection with values start, start + step, ... up to, but excluding end
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def tabulate[A](n: Int)(f: (Int) ⇒ A): Queue[A]

Produces a collection containing values of a given function over a range of integer values starting from 0.

  • n
    • The number of elements in the collection
  • f
    • The function computing element values
  • returns
    • A collection consisting of elements f(0), ..., f(n -1)
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def tabulate[A](n1: Int, n2: Int)(f: (Int, Int) ⇒ A): Queue[Queue[A]]

Produces a two-dimensional collection containing values of a given function over ranges of integer values starting from 0.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • f
    • The function computing element values
  • returns
    • A collection consisting of elements f(i1, i2) for 0 <= i1 < n1 and 0 <= i2 < n2 .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def tabulate[A](n1: Int, n2: Int, n3: Int)(f: (Int, Int, Int) ⇒ A): Queue[Queue[Queue[A]]]

Produces a three-dimensional collection containing values of a given function over ranges of integer values starting from 0.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • f
    • The function computing element values
  • returns
    • A collection consisting of elements f(i1, i2, i3) for 0 <= i1 < n1 , 0 <= i2 < n2 , and 0 <= i3 < n3 .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def tabulate[A](n1: Int, n2: Int, n3: Int, n4: Int)(f: (Int, Int, Int, Int) ⇒ A): Queue[Queue[Queue[Queue[A]]]]

Produces a four-dimensional collection containing values of a given function over ranges of integer values starting from 0.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • n4
    • the number of elements in the 4th dimension
  • f
    • The function computing element values
  • returns
    • A collection consisting of elements f(i1, i2, i3, i4) for 0 <= i1 < n1 , 0 <= i2 < n2 , 0 <= i3 < n3 , and 0 <= i4 < n4 .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

def tabulate[A](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int)(f: (Int, Int, Int, Int, Int) ⇒ A): Queue[Queue[Queue[Queue[Queue[A]]]]]

Produces a five-dimensional collection containing values of a given function over ranges of integer values starting from 0.

  • n1
    • the number of elements in the 1st dimension
  • n2
    • the number of elements in the 2nd dimension
  • n3
    • the number of elements in the 3nd dimension
  • n4
    • the number of elements in the 4th dimension
  • n5
    • the number of elements in the 5th dimension
  • f
    • The function computing element values
  • returns
    • A collection consisting of elements f(i1, i2, i3, i4, i5) for 0 <= i1 < n1 , 0 <= i2 < n2 , 0 <= i3 < n3 , 0 <= i4 < n4 , and 0 <= i5 < n5 .
  • Definition Classes
    • GenTraversableFactory

(defined at scala.collection.generic.GenTraversableFactory)

Value Members From scala.collection.generic.GenericCompanion

def apply[A](elems: A*): Queue[A]

Creates a collection with the specified elements.

  • A
    • the type of the collection’s elements
  • elems
    • the elements of the created collection
  • returns
    • a new collection with elements elems
  • Definition Classes
    • GenericCompanion

(defined at scala.collection.generic.GenericCompanion)

def empty[A]: Queue[A]

An empty collection of type CC[A]

  • A
    • the type of the collection’s elements
  • Definition Classes
    • GenericCompanion

(defined at scala.collection.generic.GenericCompanion)

Value Members From scala.collection.generic.SeqFactory

def unapplySeq[A](x: Queue[A]): Some[Queue[A]]

This method is called in a pattern match { case Seq(…) => }.

  • x
    • the selector value
  • returns
    • sequence wrapped in an option, if this is a Seq, otherwise none
  • Definition Classes
    • SeqFactory

(defined at scala.collection.generic.SeqFactory)

Value Members From scala.collection.mutable.Queue

implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Queue[A]]

(defined at scala.collection.mutable.Queue)

def newBuilder[A]: Builder[A, Queue[A]]

The default builder for Traversable objects.

  • A
    • the type of the collection’s elements
  • Definition Classes
    • Queue → GenericCompanion (defined at scala.collection.mutable.Queue)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala
package collection
package mutable

import generic._

/** `Queue` objects implement data structures that allow to
 *  insert and retrieve elements in a first-in-first-out (FIFO) manner.
 *
 *  @author  Matthias Zenger
 *  @author  Martin Odersky
 *  @version 2.8
 *  @since   1
 *  @see [[http://docs.scala-lang.org/overviews/collections/concrete-mutable-collection-classes.html#queues "Scala's Collection Library overview"]]
 *  section on `Queues` for more information.
 *
 *  @define Coll `mutable.Queue`
 *  @define coll mutable queue
 *  @define orderDependent
 *  @define orderDependentFold
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 */
class Queue[A]
extends MutableList[A]
   with LinearSeqOptimized[A, Queue[A]]
   with GenericTraversableTemplate[A, Queue]
   with Cloneable[Queue[A]]
   with Serializable
{
  override def companion: GenericCompanion[Queue] = Queue

  override protected[this] def newBuilder = companion.newBuilder[A]

  private[mutable] def this(fst: LinkedList[A], lst: LinkedList[A], lng: Int) {
    this()
    first0 = fst
    last0 = lst
    len = lng
  }

  /** Adds all elements to the queue.
   *
   *  @param  elems       the elements to add.
   */
  def enqueue(elems: A*): Unit = this ++= elems

  /** Returns the first element in the queue, and removes this element
   *  from the queue.
   *
   *  @throws java.util.NoSuchElementException
   *  @return the first element of the queue.
   */
  def dequeue(): A =
    if (isEmpty)
      throw new NoSuchElementException("queue empty")
    else {
      val res = first0.elem
      first0 = first0.next
      decrementLength()
      res
    }

  /** Returns the first element in the queue which satisfies the
   *  given predicate, and removes this element from the queue.
   *
   *  @param p   the predicate used for choosing the first element
   *  @return the first element of the queue for which p yields true
   */
  def dequeueFirst(p: A => Boolean): Option[A] =
    if (isEmpty)
      None
    else if (p(first0.elem)) {
      val res: Option[A] = Some(first0.elem)
      first0 = first0.next
      decrementLength()
      res
    } else {
      val optElem = removeFromList(p)
      if (optElem != None) decrementLength()
      optElem
    }

  private def removeFromList(p: A => Boolean): Option[A] = {
    var leftlst = first0
    var res: Option[A] = None
    while (leftlst.next.nonEmpty && !p(leftlst.next.elem)) {
      leftlst = leftlst.next
    }
    if (leftlst.next.nonEmpty) {
      res = Some(leftlst.next.elem)
      if (leftlst.next eq last0) last0 = leftlst
      leftlst.next = leftlst.next.next
    }
    res
  }

  /** Returns all elements in the queue which satisfy the
   *  given predicate, and removes those elements from the queue.
   *
   *  @param p   the predicate used for choosing elements
   *  @return    a sequence of all elements in the queue for which
   *             p yields true.
   */
  def dequeueAll(p: A => Boolean): Seq[A] = {
    if (first0.isEmpty)
      Seq.empty
    else {
      val res = new ArrayBuffer[A]
      while ((first0.nonEmpty) && p(first0.elem)) {
        res += first0.elem
        first0 = first0.next
        decrementLength()
      }
      if (first0.isEmpty) res
      else removeAllFromList(p, res)
    }
  }

  private def removeAllFromList(p: A => Boolean, res: ArrayBuffer[A]): ArrayBuffer[A] = {
    var leftlst = first0
    while (leftlst.next.nonEmpty) {
      if (p(leftlst.next.elem)) {
        res += leftlst.next.elem
        if (leftlst.next eq last0) last0 = leftlst
        leftlst.next = leftlst.next.next
        decrementLength()
      } else leftlst = leftlst.next
    }
    res
  }

  /** Return the proper suffix of this list which starts with the first element that satisfies `p`.
   *  That element is unlinked from the list. If no element satisfies `p`, return None.
   */
  @deprecated("extractFirst inappropriately exposes implementation details.  Use dequeue or dequeueAll.", "2.11.0")
  def extractFirst(start: LinkedList[A], p: A => Boolean): Option[LinkedList[A]] = {
    if (isEmpty) None
    else {
      var cell = start
      while ((cell.next.nonEmpty) && !p(cell.next.elem)) {
        cell = cell.next
      }
      if (cell.next.isEmpty)
        None
      else {
        val res: Option[LinkedList[A]] = Some(cell.next)
        cell.next = cell.next.next
        decrementLength()
        res
      }
    }
  }

  /** Returns the first element in the queue, or throws an error if there
   *  is no element contained in the queue.
   *
   *  @return the first element.
   */
  def front: A = head


  // TODO - Don't override this just for new to create appropriate type....
  override def tail: Queue[A] = {
    val tl = new Queue[A]
    tailImpl(tl)
    tl
  }

  override def clone(): Queue[A] = {
    val bf = newBuilder
    bf ++= seq
    bf.result()
  }

  private[this] def decrementLength() {
    len -= 1
    if (len == 0) last0 = first0
  }
}


object Queue extends SeqFactory[Queue] {
  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Queue[A]] = ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]

  def newBuilder[A]: Builder[A, Queue[A]] = new MutableList[A] mapResult { _.toQueue }
}