Packages

object Either extends Serializable

Source
Either.scala
Linear Supertypes
Serializable, java.io.Serializable, AnyRef, Any
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Type Members

  1. final case class LeftProjection [+A, +B](e: Either[A, B]) extends Product with Serializable

    Projects an Either into a Left.

    Projects an Either into a Left.

    This allows for-comprehensions over the left side of Either instances, reversing Either's usual right-bias.

    For example 

    for (s <- Left("flower").left) yield s.length // Left(6)

    Continuing the analogy with scala.Option, a LeftProjection declares that Left should be analogous to Some in some code.

    // using Option:
def interactWithDB(x: Query): Option[Result] =
  try {
    Some(getResultFromDatabase(x))
  } catch {
    case ex => None
  }

// this will only be executed if interactWithDB returns a Some
val report =
  for (r <- interactWithDB(someQuery)) yield generateReport(r)
if (report.isDefined)
  send(report)
else
  log("report not generated, not sure why...")
    // using Either
def interactWithDB(x: Query): Either[Exception, Result] =
  try {
    Right(getResultFromDatabase(x))
  } catch {
    case ex => Left(ex)
  }

// this will only be executed if interactWithDB returns a Right
val report =
  for (r <- interactWithDB(someQuery).right) yield generateReport(r)
if (report.isRight)
  send(report)
else
  log("report not generated, reason was " + report.left.get)
    Version

    1.0, 11/10/2008

  2. implicit final class MergeableEither [A] extends AnyVal

    Allows use of a merge method to extract values from Either instances regardless of whether they are Left or Right.

    Allows use of a merge method to extract values from Either instances regardless of whether they are Left or Right.

    val l = Left(List(1)): Either[List[Int], Vector[Int]]
val r = Right(Vector(1)): Either[List[Int], Vector[Int]]
l.merge: Seq[Int] // List(1)
r.merge: Seq[Int] // Vector(1)
  3. final case class RightProjection [+A, +B](e: Either[A, B]) extends Product with Serializable

    Projects an Either into a Right.

    Projects an Either into a Right.

    Because Either is already right-biased, this class is not normally needed. (It is retained in the library for now for easy cross-compilation between Scala 2.11 and 2.12.)

    Version

    1.0, 11/10/2008

Value Members

  1. def cond[X, Y](test: Boolean, right: ⇒ Y, left: ⇒ X): Either[X, Y]

    If the condition is satisfied, return the given B in Right, otherwise, return the given A in Left.

    If the condition is satisfied, return the given B in Right, otherwise, return the given A in Left.

    val userInput: String = ...
Either.cond(
  userInput.forall(_.isDigit) && userInput.size == 10,
  PhoneNumber(userInput),
  "The input (%s) does not look like a phone number".format(userInput)