Scala example source code file (GenericCompanion.scala)

This example Scala source code file (GenericCompanion.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, builder, cc, coll, genericcompanion, gentraversable

The GenericCompanion.scala Scala example source code

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

package scala
package collection
package generic

import mutable.Builder
import scala.language.higherKinds

/** A template class for companion objects of "regular" collection classes
 *  represent an unconstrained higher-kinded type. Typically
 *  such classes inherit from trait `GenericTraversableTemplate`.
 *  @tparam  CC   The type constructor representing the collection class.
 *  @see [[scala.collection.generic.GenericTraversableTemplate]]
 *  @author Martin Odersky
 *  @since 2.8
 *  @define coll  collection
 *  @define Coll  `CC`
 */
abstract class GenericCompanion[+CC[X] <: GenTraversable[X]] {
  /** The underlying collection type with unknown element type */
  protected[this] type Coll = CC[_]

  /** The default builder for `$Coll` objects.
   *  @tparam A      the type of the ${coll}'s elements
   */
  def newBuilder[A]: Builder[A, CC[A]]

  /** An empty collection of type `$Coll[A]`
   *  @tparam A      the type of the ${coll}'s elements
   */
  def empty[A]: CC[A] = newBuilder[A].result()

  /** Creates a $coll with the specified elements.
   *  @tparam A      the type of the ${coll}'s elements
   *  @param elems  the elements of the created $coll
   *  @return a new $coll with elements `elems`
   */
  def apply[A](elems: A*): CC[A] = {
    if (elems.isEmpty) empty[A]
    else {
      val b = newBuilder[A]
      b ++= elems
      b.result()
    }
  }
}