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
  • package concurrent

    This package object contains primitives for concurrent and parallel programming.

    This package object contains primitives for concurrent and parallel programming.

    Guide

    A more detailed guide to Futures and Promises, including discussion and examples can be found at https://docs.scala-lang.org/overviews/core/futures.html.

    Common Imports

    When working with Futures, you will often find that importing the whole concurrent package is convenient:

    import scala.concurrent._

    When using things like Futures, it is often required to have an implicit ExecutionContext in scope. The general advice for these implicits are as follows.

    If the code in question is a class or method definition, and no ExecutionContext is available, request one from the caller by adding an implicit parameter list:

    def myMethod(myParam: MyType)(implicit ec: ExecutionContext) = …
//Or
class MyClass(myParam: MyType)(implicit ec: ExecutionContext) { … }

    This allows the caller of the method, or creator of the instance of the class, to decide which ExecutionContext should be used.

    For typical REPL usage and experimentation, importing the global ExecutionContext is often desired.

    import scala.concurrent.ExcutionContext.Implicits.global

    Specifying Durations

    Operations often require a duration to be specified. A duration DSL is available to make defining these easier:

    import scala.concurrent.duration._
val d: Duration = 10.seconds

    Using Futures For Non-blocking Computation

    Basic use of futures is easy with the factory method on Future, which executes a provided function asynchronously, handing you back a future result of that function without blocking the current thread. In order to create the Future you will need either an implicit or explicit ExecutionContext to be provided:

    import scala.concurrent._
import ExecutionContext.Implicits.global  // implicit execution context

val firstZebra: Future[Int] = Future {
  val words = Files.readAllLines("/etc/dictionaries-common/words").asScala
  words.indexOfSlice("zebra")
}

    Avoid Blocking

    Although blocking is possible in order to await results (with a mandatory timeout duration):

    import scala.concurrent.duration._
Await.result(firstZebra, 10.seconds)

    and although this is sometimes necessary to do, in particular for testing purposes, blocking in general is discouraged when working with Futures and concurrency in order to avoid potential deadlocks and improve performance. Instead, use callbacks or combinators to remain in the future domain:

    val animalRange: Future[Int] = for {
  aardvark <- firstAardvark
  zebra <- firstZebra
} yield zebra - aardvark

animalRange.onSuccess {
  case x if x > 500000 => println("It's a long way from Aardvark to Zebra")
}
    Definition Classes
    scala
  • package duration
    Definition Classes
    concurrent
  • object Deadline extends java.io.Serializable
    Definition Classes
    duration
  • DeadlineIsOrdered

implicit object DeadlineIsOrdered extends Ordering[Deadline]

The natural ordering for deadline is determined by the natural order of the underlying (finite) duration.

Source
Deadline.scala
Linear Supertypes
math.Ordering[Deadline], math.PartialOrdering[Deadline], math.Equiv[Deadline], java.io.Serializable, Comparator[Deadline], AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. DeadlineIsOrdered
  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(a: Deadline, b: Deadline): 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
    DeadlineIsOrdered → Ordering → Comparator
  2. def equiv(x: Deadline, y: Deadline): 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: Deadline, y: Deadline): 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: Deadline, y: Deadline): 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: Deadline, y: Deadline): 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: Deadline, y: Deadline): 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 <: Deadline](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 <: Deadline](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: Deadline): 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) => Deadline): 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[Deadline]): math.Ordering[Deadline]

    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: (Deadline) => S)(implicit ord: math.Ordering[S]): math.Ordering[Deadline]

    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[Deadline]

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