Packages

  • package root

    This is the documentation for the Scala standard library.

    This is the documentation for the Scala standard library.

    Package structure

    The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.

    Notable packages include:

    Other packages exist. See the complete list on the right.

    Additional parts of the standard library are shipped as separate libraries. These include:

    Automatic imports

    Identifiers in the scala package and the scala.Predef object are always in scope by default.

    Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example, List is an alias for scala.collection.immutable.List.

    Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.

    Definition Classes
    root
  • package scala

    Core Scala types.

    Core Scala types. They are always available without an explicit import.

    Definition Classes
    root
  • abstract class Enumeration extends Serializable

    Defines a finite set of values specific to the enumeration.

    Defines a finite set of values specific to the enumeration. Typically these values enumerate all possible forms something can take and provide a lightweight alternative to case classes.

    Each call to a Value method adds a new unique value to the enumeration. To be accessible, these values are usually defined as val members of the enumeration.

    All values in an enumeration share a common, unique type defined as the Value type member of the enumeration (Value selected on the stable identifier path of the enumeration instance).

    Values SHOULD NOT be added to an enumeration after its construction; doing so makes the enumeration thread-unsafe. If values are added to an enumeration from multiple threads (in a non-synchronized fashion) after construction, the behavior of the enumeration is undefined.

    Definition Classes
    scala
    Annotations
    @SerialVersionUID()
    Examples:

    1. // Define a new enumeration with a type alias and work with the full set of enumerated values
object WeekDay extends Enumeration {
  type WeekDay = Value
  val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
}
import WeekDay._

def isWorkingDay(d: WeekDay) = ! (d == Sat || d == Sun)

WeekDay.values filter isWorkingDay foreach println
// output:
// Mon
// Tue
// Wed
// Thu
// Fri
      2. , 

    2. // Example of adding attributes to an enumeration by extending the Enumeration.Val class
object Planet extends Enumeration {
  protected case class PlanetVal(mass: Double, radius: Double) extends super.Val {
    def surfaceGravity: Double = Planet.G * mass / (radius * radius)
    def surfaceWeight(otherMass: Double): Double = otherMass * surfaceGravity
  }
  import scala.language.implicitConversions
  implicit def valueToPlanetVal(x: Value): PlanetVal = x.asInstanceOf[PlanetVal]

  val G: Double = 6.67300E-11
  val Mercury = PlanetVal(3.303e+23, 2.4397e6)
  val Venus   = PlanetVal(4.869e+24, 6.0518e6)
  val Earth   = PlanetVal(5.976e+24, 6.37814e6)
  val Mars    = PlanetVal(6.421e+23, 3.3972e6)
  val Jupiter = PlanetVal(1.9e+27, 7.1492e7)
  val Saturn  = PlanetVal(5.688e+26, 6.0268e7)
  val Uranus  = PlanetVal(8.686e+25, 2.5559e7)
  val Neptune = PlanetVal(1.024e+26, 2.4746e7)
}

println(Planet.values.filter(_.radius > 7.0e6))
// output:
// Planet.ValueSet(Jupiter, Saturn, Uranus, Neptune)
  • Val
  • Value
  • ValueOrdering
  • ValueSet
o

scala.Enumeration

ValueOrdering

implicit object ValueOrdering extends Ordering[Value]

An ordering by id for values of this set

Source
Enumeration.scala
Linear Supertypes
math.Ordering[Value], math.PartialOrdering[Value], math.Equiv[Value], java.io.Serializable, Comparator[Value], AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. ValueOrdering
  2. Ordering
  3. PartialOrdering
  4. Equiv
  5. Serializable
  6. Comparator
  7. AnyRef
  8. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Type Members

  1. class OrderingOps extends AnyRef

    This inner class defines comparison operators available for T.

    This inner class defines comparison operators available for T.

    It can't extend AnyVal because it is not a top-level class or a member of a statically accessible object.

    Definition Classes
    Ordering

Value Members

  1. def compare(x: Value, y: Value): Int

    Returns an integer whose sign communicates how x compares to y.

    Returns an integer whose sign communicates how x compares to y.

    The result sign has the following meaning:

    • negative if x < y
    • positive if x > y
    • zero otherwise (if x == y)
    Definition Classes
    ValueOrdering → Ordering → Comparator
  2. def equiv(x: Value, y: Value): Boolean

    Return true if x == y in the ordering.

    Return true if x == y in the ordering.

    Definition Classes
    Ordering → PartialOrdering → Equiv
  3. def gt(x: Value, y: Value): Boolean

    Return true if x > y in the ordering.

    Return true if x > y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  4. def gteq(x: Value, y: Value): Boolean

    Return true if x >= y in the ordering.

    Return true if x >= y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  5. def isReverseOf(other: math.Ordering[_]): Boolean

    Returns whether or not the other ordering is the opposite ordering of this one.

    Returns whether or not the other ordering is the opposite ordering of this one.

    Equivalent to other == this.reverse.

    Implementations should only override this method if they are overriding reverse as well.

    Definition Classes
    Ordering
  6. def lt(x: Value, y: Value): Boolean

    Return true if x < y in the ordering.

    Return true if x < y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  7. def lteq(x: Value, y: Value): Boolean

    Return true if x <= y in the ordering.

    Return true if x <= y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  8. def max[U <: Value](x: U, y: U): U

    Return x if x >= y, otherwise y.

    Return x if x >= y, otherwise y.

    Definition Classes
    Ordering
  9. def min[U <: Value](x: U, y: U): U

    Return x if x <= y, otherwise y.

    Return x if x <= y, otherwise y.

    Definition Classes
    Ordering
  10. implicit def mkOrderingOps(lhs: Value): OrderingOps

    This implicit method augments T with the comparison operators defined in scala.math.Ordering.Ops.

    This implicit method augments T with the comparison operators defined in scala.math.Ordering.Ops.

    Definition Classes
    Ordering
  11. def on[U](f: (U) => Value): math.Ordering[U]

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

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

    def compare(x:U, y:U) = Ordering[T].compare(f(x), f(y))
    Definition Classes
    Ordering
  12. def orElse(other: math.Ordering[Value]): math.Ordering[Value]

    Creates an Ordering[T] whose compare function returns the result of this Ordering's compare function, if it is non-zero, or else the result of others compare function.

    Creates an Ordering[T] whose compare function returns the result of this Ordering's compare function, if it is non-zero, or else the result of others compare function.

    other

    an Ordering to use if this Ordering returns zero

    Definition Classes
    Ordering
    Example:

    1. case class Pair(a: Int, b: Int)

val pairOrdering = Ordering.by[Pair, Int](_.a)
                           .orElse(Ordering.by[Pair, Int](_.b))
  13. def orElseBy[S](f: (Value) => S)(implicit ord: math.Ordering[S]): math.Ordering[Value]

    Given f, a function from T into S, creates an Ordering[T] whose compare function returns the result of this Ordering's compare function, if it is non-zero, or else a result equivalent to:

    Given f, a function from T into S, creates an Ordering[T] whose compare function returns the result of this Ordering's compare function, if it is non-zero, or else a result equivalent to:

    Ordering[S].compare(f(x), f(y))

    This function is equivalent to passing the result of Ordering.by(f) to orElse.

    Definition Classes
    Ordering
    Example:

    1. case class Pair(a: Int, b: Int)

val pairOrdering = Ordering.by[Pair, Int](_.a)
                           .orElseBy[Int](_.b)
  14. def reverse: math.Ordering[Value]

    Return the opposite ordering of this one.

    Return the opposite ordering of this one.

    Implementations overriding this method MUST override isReverseOf as well if they change the behavior at all (for example, caching does not require overriding it).

    Definition Classes
    Ordering → PartialOrdering
  15. def reversed(): Comparator[Value]
    Definition Classes
    Comparator
  16. def thenComparing[U <: Comparable[_ >: U <: AnyRef]](arg0: java.util.function.Function[_ >: Value <: AnyRef, _ <: U]): Comparator[Value]
    Definition Classes
    Comparator
  17. def thenComparing[U <: AnyRef](arg0: java.util.function.Function[_ >: Value <: AnyRef, _ <: U], arg1: Comparator[_ >: U <: AnyRef]): Comparator[Value]
    Definition Classes
    Comparator
  18. def thenComparing(arg0: Comparator[_ >: Value <: AnyRef]): Comparator[Value]
    Definition Classes
    Comparator
  19. def thenComparingDouble(arg0: ToDoubleFunction[_ >: Value <: AnyRef]): Comparator[Value]
    Definition Classes
    Comparator
  20. def thenComparingInt(arg0: ToIntFunction[_ >: Value <: AnyRef]): Comparator[Value]
    Definition Classes
    Comparator
  21. def thenComparingLong(arg0: ToLongFunction[_ >: Value <: AnyRef]): Comparator[Value]
    Definition Classes
    Comparator
  22. def tryCompare(x: Value, y: Value): Some[Int]

    Returns whether a comparison between x and y is defined, and if so the result of compare(x, y).

    Returns whether a comparison between x and y is defined, and if so the result of compare(x, y).

    Definition Classes
    Ordering → PartialOrdering