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**     ________ ___   / /  ___     Scala API                            **
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package scala.math

/** A class for partially ordered data.
 *
 *  @author  Martin Odersky
 *  @version 1.0, 23/04/2004
 */
trait PartiallyOrdered[+A] {

  /** Result of comparing this with operand that.
   *  Returns None if operands are not comparable.
   *  If operands are comparable, returns Some(x) where
   *  x < 0    iff    this < that
   *  x == 0   iff    this == that
   *  x > 0    iff    this > that
   */
  def tryCompareTo [B >: A <% PartiallyOrdered[B]](that: B): Option[Int]

  def <  [B >: A <% PartiallyOrdered[B]](that: B): Boolean =
    (this tryCompareTo that) match {
      case Some(x) if x < 0 => true
      case _ => false
    }
  def >  [B >: A <% PartiallyOrdered[B]](that: B): Boolean =
    (this tryCompareTo that) match {
      case Some(x) if x > 0 => true
      case _ => false
    }
  def <= [B >: A <% PartiallyOrdered[B]](that: B): Boolean =
    (this tryCompareTo that) match {
      case Some(x) if x <= 0 => true
      case _ => false
    }
  def >= [B >: A <% PartiallyOrdered[B]](that: B): Boolean =
    (this tryCompareTo that) match {
      case Some(x) if x >= 0 => true
      case _ => false
    }
}