Packages

object Ordering extends LowPriorityOrderingImplicits with java.io.Serializable

This is the companion object for the scala.math.Ordering trait.

It contains many implicit orderings as well as well as methods to construct new orderings.

Source
Ordering.scala
Content Hierarchy
Ordering
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Inherited
  1. Ordering
  2. Serializable
  3. LowPriorityOrderingImplicits
  4. AnyRef
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Visibility
  1. Public
  2. Protected

Type Members

  1. type AsComparable[A] = (A) => Comparable[_ >: A]
  2. trait BigDecimalOrdering extends Ordering[BigDecimal]
  3. trait BigIntOrdering extends Ordering[BigInt]
  4. trait BooleanOrdering extends Ordering[Boolean]
  5. trait ByteOrdering extends Ordering[Byte]
  6. sealed trait CachedReverse[T] extends Ordering[T]

    An ordering which caches the value of its reverse.

  7. trait CharOrdering extends Ordering[Char]
  8. trait ExtraImplicits extends AnyRef
  9. trait IntOrdering extends Ordering[Int]
  10. trait LongOrdering extends Ordering[Long]
  11. trait OptionOrdering[T] extends Ordering[Option[T]]
  12. trait ShortOrdering extends Ordering[Short]
  13. trait StringOrdering extends Ordering[String]
  14. trait SymbolOrdering extends Ordering[Symbol]
  15. trait UnitOrdering extends Ordering[Unit]

Value Members

  1. implicit def Option[T](implicit ord: Ordering[T]): Ordering[Option[T]]
  2. implicit def Tuple2[T1, T2](implicit ord1: Ordering[T1], ord2: Ordering[T2]): Ordering[(T1, T2)]
  3. implicit def Tuple3[T1, T2, T3](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3]): Ordering[(T1, T2, T3)]
  4. implicit def Tuple4[T1, T2, T3, T4](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4]): Ordering[(T1, T2, T3, T4)]
  5. implicit def Tuple5[T1, T2, T3, T4, T5](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5]): Ordering[(T1, T2, T3, T4, T5)]
  6. implicit def Tuple6[T1, T2, T3, T4, T5, T6](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6]): Ordering[(T1, T2, T3, T4, T5, T6)]
    Annotations
    @SerialVersionUID()
  7. implicit def Tuple7[T1, T2, T3, T4, T5, T6, T7](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7]): Ordering[(T1, T2, T3, T4, T5, T6, T7)]
  8. implicit def Tuple8[T1, T2, T3, T4, T5, T6, T7, T8](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7], ord8: Ordering[T8]): Ordering[(T1, T2, T3, T4, T5, T6, T7, T8)]
    Annotations
    @SerialVersionUID()
  9. implicit def Tuple9[T1, T2, T3, T4, T5, T6, T7, T8, T9](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7], ord8: Ordering[T8], ord9: Ordering[T9]): Ordering[(T1, T2, T3, T4, T5, T6, T7, T8, T9)]
    Annotations
    @SerialVersionUID()
  10. def apply[T](implicit ord: Ordering[T]): Ordering[T]
    Annotations
    @inline()
  11. def by[T, S](f: (T) => S)(implicit ord: Ordering[S]): Ordering[T]

    Given f, a function from T into S, creates an Ordering[T] whose compare function is equivalent to:

    Given f, a function from T into S, creates an Ordering[T] whose compare function is equivalent to:

    def compare(x:T, y:T) = Ordering[S].compare(f(x), f(y))

    This function is an analogue to Ordering.on where the Ordering[S] parameter is passed implicitly.

  12. implicit def comparatorToOrdering[A](implicit cmp: Comparator[A]): Ordering[A]
  13. def fromLessThan[T](cmp: (T, T) => Boolean): Ordering[T]

    Construct an Ordering[T] given a function lt.

  14. implicit def ordered[A](implicit asComparable: AsComparable[A]): Ordering[A]

    This would conflict with all the nice implicit Orderings available, but thanks to the magic of prioritized implicits via subclassing we can make Ordered[A] => Ordering[A] only turn up if nothing else works.

    This would conflict with all the nice implicit Orderings available, but thanks to the magic of prioritized implicits via subclassing we can make Ordered[A] => Ordering[A] only turn up if nothing else works. Since Ordered[A] extends Comparable[A] anyway, we can throw in some Java interop too.

    Definition Classes
    LowPriorityOrderingImplicits
  15. implicit object BigDecimal extends BigDecimalOrdering
    Annotations
    @SerialVersionUID()
  16. implicit object BigInt extends BigIntOrdering
    Annotations
    @SerialVersionUID()
  17. implicit object Boolean extends BooleanOrdering
    Annotations
    @SerialVersionUID()
  18. implicit object Byte extends ByteOrdering
    Annotations
    @SerialVersionUID()
  19. implicit object Char extends CharOrdering
    Annotations
    @SerialVersionUID()
  20. implicit object DeprecatedDoubleOrdering extends TotalOrdering
    Annotations
    @migration @SerialVersionUID()
    Migration

    (Changed in version 2.13.0) The default implicit ordering for doubles now maintains consistency between its compare method and its lt, min, equiv, etc., methods, which means nonconforming to IEEE 754's behavior for -0.0 and NaN. The sort order of doubles remains the same, however, with NaN at the end. Import Ordering.Double.IeeeOrdering to recover the previous behavior. See also https://www.scala-lang.org/api/current/scala/math/Ordering$$Double$.html.

  21. implicit object DeprecatedFloatOrdering extends TotalOrdering
    Annotations
    @migration @SerialVersionUID()
    Migration

    (Changed in version 2.13.0) The default implicit ordering for floats now maintains consistency between its compare method and its lt, min, equiv, etc., methods, which means nonconforming to IEEE 754's behavior for -0.0F and NaN. The sort order of floats remains the same, however, with NaN at the end. Import Ordering.Float.IeeeOrdering to recover the previous behavior. See also https://www.scala-lang.org/api/current/scala/math/Ordering$$Float$.html.

  22. object Double

    Orderings for Doubles.

    Orderings for Doubles.

    The behavior of the comparison operations provided by the default (implicit) ordering on Double changed in 2.10.0 and 2.13.0. Prior to Scala 2.10.0, the Ordering instance used semantics consistent with java.lang.Double.compare.

    Scala 2.10.0 changed the implementation of lt, equiv, min, etc., to be IEEE 754 compliant, while keeping the compare method NOT compliant, creating an internally inconsistent instance. IEEE 754 specifies that 0.0 == -0.0. In addition, it requires all comparisons with Double.NaN return false thus 0.0 < Double.NaN, 0.0 > Double.NaN, and Double.NaN == Double.NaN all yield false, analogous None in flatMap.

    Recognizing the limitation of the IEEE 754 semantics in terms of ordering, Scala 2.13.0 created two instances: Ordering.Double.IeeeOrdering, which retains the IEEE 754 semantics from Scala 2.12.x, and Ordering.Double.TotalOrdering, which brings back the java.lang.Double.compare semantics for all operations. The default extends TotalOrdering.

    List(0.0, 1.0, 0.0 / 0.0, -1.0 / 0.0).sorted      // List(-Infinity, 0.0, 1.0, NaN)
    List(0.0, 1.0, 0.0 / 0.0, -1.0 / 0.0).min         // -Infinity
    implicitly[Ordering[Double]].lt(0.0, 0.0 / 0.0)   // true
    {
      import Ordering.Double.IeeeOrdering
      List(0.0, 1.0, 0.0 / 0.0, -1.0 / 0.0).sorted    // List(-Infinity, 0.0, 1.0, NaN)
      List(0.0, 1.0, 0.0 / 0.0, -1.0 / 0.0).min       // NaN
      implicitly[Ordering[Double]].lt(0.0, 0.0 / 0.0) // false
    }
  23. object Float

    Orderings for Floats.

    Orderings for Floats.

    The behavior of the comparison operations provided by the default (implicit) ordering on Float changed in 2.10.0 and 2.13.0. Prior to Scala 2.10.0, the Ordering instance used semantics consistent with java.lang.Float.compare.

    Scala 2.10.0 changed the implementation of lt, equiv, min, etc., to be IEEE 754 compliant, while keeping the compare method NOT compliant, creating an internally inconsistent instance. IEEE 754 specifies that 0.0F == -0.0F. In addition, it requires all comparisons with Float.NaN return false thus 0.0F < Float.NaN, 0.0F > Float.NaN, and Float.NaN == Float.NaN all yield false, analogous None in flatMap.

    Recognizing the limitation of the IEEE 754 semantics in terms of ordering, Scala 2.13.0 created two instances: Ordering.Float.IeeeOrdering, which retains the IEEE 754 semantics from Scala 2.12.x, and Ordering.Float.TotalOrdering, which brings back the java.lang.Float.compare semantics for all operations. The default extends TotalOrdering.

    List(0.0F, 1.0F, 0.0F / 0.0F, -1.0F / 0.0F).sorted      // List(-Infinity, 0.0, 1.0, NaN)
    List(0.0F, 1.0F, 0.0F / 0.0F, -1.0F / 0.0F).min         // -Infinity
    implicitly[Ordering[Float]].lt(0.0F, 0.0F / 0.0F)       // true
    {
      import Ordering.Float.IeeeOrdering
      List(0.0F, 1.0F, 0.0F / 0.0F, -1.0F / 0.0F).sorted    // List(-Infinity, 0.0, 1.0, NaN)
      List(0.0F, 1.0F, 0.0F / 0.0F, -1.0F / 0.0F).min       // NaN
      implicitly[Ordering[Float]].lt(0.0F, 0.0F / 0.0F)     // false
    }
  24. object Implicits extends ExtraImplicits

    An object containing implicits which are not in the default scope.

  25. implicit object Int extends IntOrdering with CachedReverse[Int]
    Annotations
    @SerialVersionUID()
  26. implicit object Long extends LongOrdering
    Annotations
    @SerialVersionUID()
  27. implicit object Short extends ShortOrdering
    Annotations
    @SerialVersionUID()
  28. implicit object String extends StringOrdering
    Annotations
    @SerialVersionUID()
  29. implicit object Symbol extends SymbolOrdering
    Annotations
    @SerialVersionUID()
  30. implicit object Unit extends UnitOrdering
    Annotations
    @SerialVersionUID()

Deprecated Value Members

  1. implicit def Iterable[T](implicit ord: Ordering[T]): Ordering[Iterable[T]]

    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Iterables are not guaranteed to have a consistent order; if using a type with a consistent order (e.g. Seq), use its Ordering (found in the Ordering.Implicits object)