Scala example source code file (BufferLike.scala)

This example Scala source code file (BufferLike.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, annotation, buffer, gentraversableonce, include, int, remove, this, traversableonce, update, use

The BufferLike.scala Scala example source code

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



package scala
package collection
package mutable

import generic._
import script._
import scala.annotation.{migration, bridge}

/** A template trait for buffers of type `Buffer[A]`.
 *
 *  Buffers are used to create sequences of elements incrementally by
 *  appending, prepending, or inserting new elements. It is also
 *  possible to access and modify elements in a random access fashion
 *  via the index of the element in the current sequence.
 *
 *  @tparam A    the type of the elements of the buffer
 *  @tparam This the type of the buffer itself.
 *
 *  $buffernote
 *
 *  @author  Martin Odersky
 *  @author  Matthias Zenger
 *  @version 2.8
 *  @since   2.8
 *  @define buffernote @note
 *    This trait provides most of the operations of a `Buffer` independently of its representation.
 *    It is typically inherited by concrete implementations of buffers.
 *
 *    To implement a concrete buffer, you need to provide implementations of the
 *    following methods:
 *    {{{
 *       def apply(idx: Int): A
 *       def update(idx: Int, elem: A)
 *       def length: Int
 *       def clear()
 *       def +=(elem: A): this.type
 *       def +=:(elem: A): this.type
 *       def insertAll(n: Int, iter: Traversable[A])
 *       def remove(n: Int): A
 *    }}}
 *  @define coll buffer
 *  @define Coll Buffer
 *  @define add  append
 *  @define Add  Append
 *  @define willNotTerminateInf
 *  @define mayNotTerminateInf
 *  @define compatMutate
 *  Note that for backward compatibility reasons, this method
 *  mutates the collection in place, unlike similar but
 *  undeprecated methods throughout the collections hierarchy.
 */
trait BufferLike[A, +This <: BufferLike[A, This] with Buffer[A]]
                extends Growable[A]
                   with Shrinkable[A]
                   with Scriptable[A]
                   with Subtractable[A, This]
                   with SeqLike[A, This]
                   with scala.Cloneable
{ self : This =>

  // Abstract methods from Seq:

  def apply(n: Int): A
  def update(n: Int, newelem: A)
  def length: Int

  // Abstract methods from Growable:

  def +=(elem: A): this.type
  def clear()

  // Abstract methods new in this class:

  /** Prepends a single element to this buffer.
   *  @param elem  the element to prepend.
   *  @return      the buffer itself.
   */
  def +=:(elem: A): this.type

  /** Inserts new elements at a given index into this buffer.
   *
   *  @param n      the index where new elements are inserted.
   *  @param elems  the traversable collection containing the elements to insert.
   *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
   *            `0 <= n <= length`.
   */
  def insertAll(n: Int, elems: scala.collection.Traversable[A])

   /** Removes the element at a given index from this buffer.
    *
    *  @param n  the index which refers to the element to delete.
    *  @return   the previous element at index `n`
    *   @throws   IndexOutOfBoundsException if the if the index `n` is not in the valid range
    *            `0 <= n < length`.
    */
  def remove(n: Int): A

  /** Removes a number of elements from a given index position.
   *
   *  @param n  the index which refers to the first element to remove.
   *  @param count  the number of elements to remove.
   *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
   *            `0 <= n <= length - count`.
   *  @throws   IllegalArgumentException if `count < 0`.
   */
  def remove(n: Int, count: Int) {
    for (i <- 0 until count) remove(n)
  }

  /** Removes a single element from this buffer, at its first occurrence.
   *  If the buffer does not contain that element, it is unchanged.
   *
   *  @param x  the element to remove.
   *  @return   the buffer itself
   */
  def -= (x: A): this.type = {
    val i = indexOf(x)
    if (i != -1) remove(i)
    this
  }

  /** Prepends elements to this buffer.
   *
   *  @param xs  the TraversableOnce containing the elements to prepend.
   *  @return the buffer itself.
   */
  def ++=:(xs: TraversableOnce[A]): this.type = { insertAll(0, xs.toTraversable); this }

  /** Appends the given elements to this buffer.
   *
   *  @param elems  the elements to append.
   */
  def append(elems: A*) { appendAll(elems) }

  /** Appends the elements contained in a traversable object to this buffer.
   *  @param xs  the traversable object containing the elements to append.
   */
  def appendAll(xs: TraversableOnce[A]) { this ++= xs }

  /** Prepends given elements to this buffer.
   *  @param elems  the elements to prepend.
   */
  def prepend(elems: A*) { prependAll(elems) }

  /** Prepends the elements contained in a traversable object to this buffer.
   *  @param xs  the collection containing the elements to prepend.
   */
  def prependAll(xs: TraversableOnce[A]) { xs ++=: this }

  /** Inserts new elements at a given index into this buffer.
   *
   *  @param n      the index where new elements are inserted.
   *  @param elems  the traversable collection containing the elements to insert.
   *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
   *            `0 <= n <= length`.
   */
  def insert(n: Int, elems: A*) { insertAll(n, elems) }

  /** Removes the first ''n'' elements of this buffer.
   *
   *  @param n  the number of elements to remove from the beginning
   *            of this buffer.
   */
  def trimStart(n: Int) { remove(0, n) }

  /** Removes the last ''n'' elements of this buffer.
   *
   *  @param n  the number of elements to remove from the end
   *            of this buffer.
   */
  def trimEnd(n: Int) { remove(length - n max 0, n) }

  /** Send a message to this scriptable object.
   *
   *  @param cmd  the message to send.
   */
  @deprecated("Scripting is deprecated.", "2.11.0")
  def <<(cmd: Message[A]): Unit = cmd match {
    case Include(Start, x)      => prepend(x)
    case Include(End, x)        => append(x)
    case Include(Index(n), x)   => insert(n, x)
    case Include(NoLo, x)       => this += x

    case Update(Start, x)       => update(0, x)
    case Update(End, x)         => update(length - 1, x)
    case Update(Index(n), x)    => update(n, x)

    case Remove(Start, x)       => if (this(0) == x) remove(0)
    case Remove(End, x)         => if (this(length - 1) == x) remove(length - 1)
    case Remove(Index(n), x)    => if (this(n) == x) remove(n)
    case Remove(NoLo, x)        => this -= x

    case Reset()                => clear()
    case s: Script[_]           => s.iterator foreach <<
    case _                      => throw new UnsupportedOperationException("message " + cmd + " not understood")
  }

  /** Defines the prefix of this object's `toString` representation.
   *  @return  a string representation which starts the result of `toString` applied to this set.
   *           Unless overridden this is simply `"Buffer"`.
   */
  override def stringPrefix: String = "Buffer"

  /** Returns the current evolving(!) state of this buffer as a read-only sequence.
   *
   *  @return  A sequence that forwards to this buffer for all its operations.
   */
  @deprecated("The returned sequence changes as this buffer is mutated. For an immutable copy, use, e.g., toList.", "2.11.0")
  def readOnly: scala.collection.Seq[A] = toSeq

  /** Creates a new collection containing both the elements of this collection and the provided
   *  traversable object.
   *
   *  @param xs     the traversable object.
   *  @return       a new collection consisting of all the elements of this collection and `xs`.
   */
  @migration("`++` creates a new buffer. Use `++=` to add an element from this buffer and return that buffer itself.", "2.8.0")
  def ++(xs: GenTraversableOnce[A]): This = clone() ++= xs.seq

  /** Creates a new collection with all the elements of this collection except `elem`.
   *
   *  @param elem  the element to remove.
   *  @return      a new collection consisting of all the elements of this collection except `elem`.
   */
  @migration("`-` creates a new buffer. Use `-=` to remove an element from this buffer and return that buffer itself.", "2.8.0")
  override def -(elem: A): This = clone() -= elem

  /** Creates a new collection with all the elements of this collection except the two
   *  or more specified elements.
   *
   *  @param elem1 the first element to remove.
   *  @param elem2 the second element to remove.
   *  @param elems the remaining elements to remove.
   *  @return      a new collection consisting of all the elements of this collection except
   *               `elem1`, `elem2` and those in `elems`.
   */
  @migration("`-` creates a new buffer. Use `-=` to remove an element from this buffer and return that buffer itself.", "2.8.0")
  override def -(elem1: A, elem2: A, elems: A*): This = clone() -= elem1 -= elem2 --= elems

  /** Creates a new collection with all the elements of this collection except those
   *  provided by the specified traversable object.
   *
   *  @param xs       the traversable object.
   *  @return         a new collection with all the elements of this collection except
   *                  those in `xs`
   */
  @migration("`--` creates a new buffer. Use `--=` to remove an element from this buffer and return that buffer itself.", "2.8.0")
  override def --(xs: GenTraversableOnce[A]): This = clone() --= xs.seq

  /** Return a clone of this buffer.
   *
   *  @return a `Buffer` with the same elements.
   */
  override def clone(): This = {
    val bf = newBuilder
    bf ++= this
    bf.result().asInstanceOf[This]
  }
}