Scala 3/scala/scala.math/Ordering/Double

Double

scala.math.Ordering.Double

object Double

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
}

Attributes

Source: Ordering.scala
Graph
Supertypes: class Object

trait Matchable

class Any
Self type: Double.type

Members list

Type members

Classlikes

Attributes

Companion: trait
Source: Ordering.scala
Supertypes: trait IeeeOrdering

trait Ordering[Double]

trait PartialOrdering[Double]

trait Equiv[Double]

trait Serializable

trait Comparator[Double]

class Object

trait Matchable

class Any
Show all
Self type: IeeeOrdering.type

An ordering for Doubles which is consistent with IEEE specifications whenever possible.

lt, lteq, equiv, gteq and gt are consistent with primitive comparison operations for Doubles, and return false when called with NaN.
min and max are consistent with math.min and math.max, and return NaN when called with NaN as either argument.
compare behaves the same as java.lang.Double.compare.

Because the behavior of Doubles specified by IEEE is not consistent with a total ordering when dealing with NaN, there are two orderings defined for Double: TotalOrdering, which is consistent with a total ordering, and IeeeOrdering, which is consistent as much as possible with IEEE spec and floating point operations defined in scala.math.

This ordering may be preferable for numeric contexts.

Attributes

See also: TotalOrdering
Companion: object
Source: Ordering.scala
Supertypes: trait Ordering[Double]

trait PartialOrdering[Double]

trait Equiv[Double]

trait Serializable

trait Comparator[Double]

class Object

trait Matchable

class Any
Show all
Known subtypes: object DoubleIsFractional

object IeeeOrdering

Attributes

Companion: trait
Source: Ordering.scala
Supertypes: trait TotalOrdering

trait Ordering[Double]

trait PartialOrdering[Double]

trait Equiv[Double]

trait Serializable

trait Comparator[Double]

class Object

trait Matchable

class Any
Show all
Self type: TotalOrdering.type

An ordering for Doubles which is a fully consistent total ordering, and treats NaN as larger than all other Double values; it behaves the same as java.lang.Double.compare.

This ordering may be preferable for sorting collections.

Attributes

See also: IeeeOrdering
Companion: object
Source: Ordering.scala
Supertypes: trait Ordering[Double]

trait PartialOrdering[Double]

trait Equiv[Double]

trait Serializable

trait Comparator[Double]

class Object

trait Matchable

class Any
Show all
Known subtypes: object DeprecatedDoubleOrdering

object TotalOrdering

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