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Scala example source code file (Ordered.scala)

This example Scala source code file (Ordered.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

a, a, boolean, boolean, int, int, ordered, ordered, ordering, t

The Scala Ordered.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.math

/** A trait for totally ordered data.
 *
 * Note that since version 2006-07-24 this trait is no longer covariant in a.
 *
 * It is important that the equals method for an instance of 
 * Ordered[A] be consistent with the compare method.  However, 
 * due to limitations inherent in the type erasure semantics, 
 * there is no reasonable way to provide a default implementation
 * of equality for instances of Ordered[A].  Therefore, if you need
 * to be able to use equality on an instance of Ordered[A] you must 
 * provide it yourself either when inheriting or instantiating. 
 *
 * It is important that the hashCode method for an instance of 
 * Ordered[A] be consistent with the compare method. However, 
 * it is not possible to provide a sensible default implementation.
 * Therefore, if you need to be able compute the hash of an 
 * instance of Ordered[A] you must provide it yourself either when 
 * inheriting or instantiating. 
 *
 *  @author  Martin Odersky
 *  @version 1.1, 2006-07-24 
 */
trait Ordered[A] extends java.lang.Comparable[A] {

  /** Result of comparing <code>this with operand that.
   *  returns <code>x where
   *  <code>x < 0    iff    this < that
   *  <code>x == 0   iff    this == that
   *  <code>x > 0    iff    this > that
   */
  def compare(that: A): Int

  def <  (that: A): Boolean = (this compare that) <  0
  def >  (that: A): Boolean = (this compare that) >  0
  def <= (that: A): Boolean = (this compare that) <= 0
  def >= (that: A): Boolean = (this compare that) >= 0
  def compareTo(that: A): Int = compare(that)
}

object Ordered {  
  /** Lens from Ordering[T] to Ordered[T] */
  implicit def orderingToOrdered[T](x: T)(implicit ord: Ordering[T]): Ordered[T] = 
    new Ordered[T] { def compare(that: T): Int = ord.compare(x, that) }
}

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