Scala example source code file (AnyVal.scala)

This example Scala source code file (AnyVal.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

any, anyval, class

The AnyVal.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala

/** `AnyVal` is the root class of all ''value types'', which describe values
 *  not implemented as objects in the underlying host system. Value classes
 *  are specified in Scala Language Specification, section 12.2.
 *
 *  The standard implementation includes nine `AnyVal` subtypes:
 *
 *  [[scala.Double]], [[scala.Float]], [[scala.Long]], [[scala.Int]], [[scala.Char]],
 *  [[scala.Short]], and [[scala.Byte]] are the ''numeric value types''.
 *
 *  [[scala.Unit]] and [[scala.Boolean]] are the ''non-numeric value types''.
 *
 *  Other groupings:
 *
 *   - The ''subrange types'' are [[scala.Byte]], [[scala.Short]], and [[scala.Char]].
 *   - The ''integer types'' include the subrange types as well as [[scala.Int]] and [[scala.Long]].
 *   - The ''floating point types'' are [[scala.Float]] and [[scala.Double]].
 *
 * Prior to Scala 2.10, `AnyVal` was a sealed trait. Beginning with Scala 2.10,
 * however, it is possible to define a subclass of `AnyVal` called a ''user-defined value class''
 * which is treated specially by the compiler. Properly-defined user value classes provide a way
 * to improve performance on user-defined types by avoiding object allocation at runtime, and by
 * replacing virtual method invocations with static method invocations.
 *
 * User-defined value classes which avoid object allocation...
 *
 *   - must have a single `val` parameter that is the underlying runtime representation.
 *   - can define `def`s, but no `val`s, `var`s, or nested `traits`s, `class`es or `object`s.
 *   - typically extend no other trait apart from `AnyVal`.
 *   - cannot be used in type tests or pattern matching.
 *   - may not override `equals` or `hashCode` methods.
 *
 * A minimal example:
 * {{{
 *     class Wrapper(val underlying: Int) extends AnyVal {
 *       def foo: Wrapper = new Wrapper(underlying * 19)
 *     }
 * }}}
 *
 * It's important to note that user-defined value classes are limited, and in some circumstances,
 * still must allocate a value class instance at runtime. These limitations and circumstances are
 * explained in greater detail in the [[http://docs.scala-lang.org/overviews/core/value-classes.html Value Classes Guide]]
 * as well as in [[http://docs.scala-lang.org/sips/pending/value-classes.html SIP-15: Value Classes]],
 * the Scala Improvement Proposal.
 */
abstract class AnyVal extends Any {
  def getClass(): Class[_ <: AnyVal] = null
}