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Scala 3/scala/scala.util/Right

Right

scala.util.Right
final case class Right[+A, +B](value: B) extends Either[A, B]

The right side of the disjoint union, as opposed to the scala.util.Left side.

Attributes

Source
Either.scala
Graph
Supertypes
class Either[A, B]
trait Serializable
trait Product
trait Equals
class Object
trait Matchable
class Any
Show all

Members list

Value members

Concrete methods

def isLeft: Boolean

Returns true if this is a Left, false otherwise.

Returns true if this is a Left, false otherwise.

Left("tulip").isLeft // true
Right("venus fly-trap").isLeft // false

Attributes

Source
Either.scala
def isRight: Boolean

Returns true if this is a Right, false otherwise.

Returns true if this is a Right, false otherwise.

Left("tulip").isRight // false
Right("venus fly-trap").isRight // true

Attributes

Source
Either.scala
def withLeft[A1 >: A]: Either[A1, B]

Upcasts this Right[A, B] to Either[A1, B]

Upcasts this Right[A, B] to Either[A1, B]

Right("x")               // Either[Nothing, String]
Right("x").withLeft[Int] // Either[Int, String]

Attributes

Source
Either.scala

Inherited methods

final def contains[B1 >: B](elem: B1): Boolean

Returns true if this is a Right and its value is equal to elem (as determined by ==), returns false otherwise.

Returns true if this is a Right and its value is equal to elem (as determined by ==), returns false otherwise.

// Returns true because value of Right is "something" which equals "something".
Right("something") contains "something"

// Returns false because value of Right is "something" which does not equal "anything".
Right("something") contains "anything"

// Returns false because it's not a Right value.
Left("something") contains "something"

Value parameters

elem

the element to test.

Attributes

Returns

true if this is a Right value equal to elem.

Inherited from:
Either
Source
Either.scala
def exists(p: B => Boolean): Boolean

Returns false if Left or returns the result of the application of the given predicate to the Right value.

Returns false if Left or returns the result of the application of the given predicate to the Right value.

Right(12).exists(_ > 10)   // true
Right(7).exists(_ > 10)    // false
Left(12).exists(_ => true) // false

Attributes

Inherited from:
Either
Source
Either.scala
def filterOrElse[A1 >: A](p: B => Boolean, zero: => A1): Either[A1, B]

Returns Right with the existing value of Right if this is a Right and the given predicate p holds for the right value, or Left(zero) if this is a Right and the given predicate p does not hold for the right value, or Left with the existing value of Left if this is a Left.

Returns Right with the existing value of Right if this is a Right and the given predicate p holds for the right value, or Left(zero) if this is a Right and the given predicate p does not hold for the right value, or Left with the existing value of Left if this is a Left.

Right(12).filterOrElse(_ > 10, -1)   // Right(12)
Right(7).filterOrElse(_ > 10, -1)    // Left(-1)
Left(7).filterOrElse(_ => false, -1) // Left(7)

Attributes

Inherited from:
Either
Source
Either.scala
def flatMap[A1 >: A, B1](f: B => Either[A1, B1]): Either[A1, B1]

Binds the given function across Right.

Binds the given function across Right.

Value parameters

f

The function to bind across Right.

Attributes

Inherited from:
Either
Source
Either.scala
def flatten[A1 >: A, B1](implicit ev: B <:< Either[A1, B1]): Either[A1, B1]

Returns the right value if this is right or this value if this is left

Returns the right value if this is right or this value if this is left

Attributes

Example 

val  l: Either[String, Either[String, Int]] = Left("pancake")
val rl: Either[String, Either[String, Int]] = Right(Left("flounder"))
val rr: Either[String, Either[String, Int]] = Right(Right(7))
l.flatten //Either[String, Int]: Left("pancake")
rl.flatten //Either[String, Int]: Left("flounder")
rr.flatten //Either[String, Int]: Right(7)

Equivalent to flatMap(id => id)

Inherited from:
Either
Source
Either.scala
def fold[C](fa: A => C, fb: B => C): C

Applies fa if this is a Left or fb if this is a Right.

Applies fa if this is a Left or fb if this is a Right.

Value parameters

fa

the function to apply if this is a Left

fb

the function to apply if this is a Right

Attributes

Returns

the results of applying the function

Example 

val result = util.Try("42".toInt).toEither
result.fold(
  e => s"Operation failed with $e",
  v => s"Operation produced value: $v"
)
Inherited from:
Either
Source
Either.scala
def forall(f: B => Boolean): Boolean

Returns true if Left or returns the result of the application of the given predicate to the Right value.

Returns true if Left or returns the result of the application of the given predicate to the Right value.

Right(12).forall(_ > 10)    // true
Right(7).forall(_ > 10)     // false
Left(12).forall(_ => false) // true

Attributes

Inherited from:
Either
Source
Either.scala
def foreach[U](f: B => U): Unit

Executes the given side-effecting function if this is a Right.

Executes the given side-effecting function if this is a Right.

Right(12).foreach(println) // prints "12"
Left(12).foreach(println)  // doesn't print

Value parameters

f

The side-effecting function to execute.

Attributes

Inherited from:
Either
Source
Either.scala
def getOrElse[B1 >: B](or: => B1): B1

Returns the value from this Right or the given argument if this is a Left.

Returns the value from this Right or the given argument if this is a Left.

Right(12).getOrElse(17) // 12
Left(12).getOrElse(17)  // 17

Attributes

Inherited from:
Either
Source
Either.scala
def joinLeft[A1 >: A, B1 >: B, C](implicit ev: A1 <:< Either[C, B1]): Either[C, B1]

Joins an Either through Left.

Joins an Either through Left.

This method requires that the left side of this Either is itself an Either type. That is, this must be some type like: 

Either[Either[C, B], B]

(which respects the type parameter bounds, shown below.)

If this instance is a Left[Either[C, B]] then the contained Either[C, B] will be returned, otherwise this value will be returned unmodified.

Left[Either[Int, String], String](Right("flower")).joinLeft // Result: Right("flower")
Left[Either[Int, String], String](Left(12)).joinLeft // Result: Left(12)
Right[Either[Int, String], String]("daisy").joinLeft // Result: Right("daisy")

This method, and joinRight, are analogous to Option#flatten.

Attributes

Inherited from:
Either
Source
Either.scala
def joinRight[A1 >: A, B1 >: B, C](implicit ev: B1 <:< Either[A1, C]): Either[A1, C]

Joins an Either through Right.

Joins an Either through Right.

This method requires that the right side of this Either is itself an Either type. That is, this must be some type like: 

Either[A, Either[A, C]]

(which respects the type parameter bounds, shown below.)

If this instance is a Right[Either[A, C]] then the contained Either[A, C] will be returned, otherwise this value will be returned unmodified.

Attributes

Example 

Right[String, Either[String, Int]](Right(12)).joinRight // Result: Right(12)
Right[String, Either[String, Int]](Left("flower")).joinRight // Result: Left("flower")
Left[String, Either[String, Int]]("flower").joinRight // Result: Left("flower")

This method, and joinLeft, are analogous to Option#flatten

Inherited from:
Either
Source
Either.scala
def left: LeftProjection[A, B]

Projects this Either as a Left.

Projects this Either as 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 _: SQLException => None
  }

// this will only be executed if interactWithDB returns a Some
val report = for (result <- interactWithDB(someQuery)) yield generateReport(result)
report match {
  case Some(r) => send(r)
  case None    => log("report not generated, not sure why...")
}

// using Either
def interactWithDB(x: Query): Either[Exception, Result] =
  try Right(getResultFromDatabase(x))
  catch {
    case e: SQLException => Left(e)
  }

 // run a report only if interactWithDB returns a Right
 val report = for (result <- interactWithDB(someQuery)) yield generateReport(result)
 report match {
   case Right(r) => send(r)
   case Left(e)  => log(s"report not generated, reason was $e")
 }
 // only report errors
 for (e <- interactWithDB(someQuery).left) log(s"query failed, reason was $e")

Attributes

Inherited from:
Either
Source
Either.scala
def map[B1](f: B => B1): Either[A, B1]

The given function is applied if this is a Right.

The given function is applied if this is a Right.

Right(12).map(x => "flower") // Result: Right("flower")
Left(12).map(x => "flower")  // Result: Left(12)

Attributes

Inherited from:
Either
Source
Either.scala
def orElse[A1 >: A, B1 >: B](or: => Either[A1, B1]): Either[A1, B1]

Returns this Right or the given argument if this is a Left.

Returns this Right or the given argument if this is a Left.

Right(1) orElse Left(2) // Right(1)
Left(1) orElse Left(2)  // Left(2)
Left(1) orElse Left(2) orElse Right(3) // Right(3)

Attributes

Inherited from:
Either
Source
Either.scala
def productElementNames: Iterator[String]

An iterator over the names of all the elements of this product.

An iterator over the names of all the elements of this product.

Attributes

Inherited from:
Product
Source
Product.scala
def productIterator: Iterator[Any]

An iterator over all the elements of this product.

An iterator over all the elements of this product.

Attributes

Returns

in the default implementation, an Iterator[Any]

Inherited from:
Product
Source
Product.scala
def swap: Either[B, A]

If this is a Left, then return the left value in Right or vice versa.

If this is a Left, then return the left value in Right or vice versa.

Attributes

Example 

val left: Either[String, Int]  = Left("left")
val right: Either[Int, String] = left.swap // Result: Right("left")


val right = Right(2)
val left  = Left(3)
for {
  r1 <- right
  r2 <- left.swap
} yield r1 * r2 // Right(6)
Inherited from:
Either
Source
Either.scala
def toOption: Option[B]

Returns a Some containing the Right value if it exists or a None if this is a Left.

Returns a Some containing the Right value if it exists or a None if this is a Left.

Right(12).toOption // Some(12)
Left(12).toOption  // None

Attributes

Inherited from:
Either
Source
Either.scala
def toSeq: Seq[B]

Returns a Seq containing the Right value if it exists or an empty Seq if this is a Left.

Returns a Seq containing the Right value if it exists or an empty Seq if this is a Left.

Right(12).toSeq // Seq(12)
Left(12).toSeq  // Seq()

Attributes

Inherited from:
Either
Source
Either.scala
def toTry(implicit ev: A <:< Throwable): Try[B]

Attributes

Inherited from:
Either
Source
Either.scala

Deprecated and Inherited methods

def right: RightProjection[A, B]

Projects this Either as a Right.

Projects this Either as a Right.

Because Either is right-biased, this method is not normally needed.

Attributes

Deprecated
[Since version 2.13.0] Either is now right-biased, use methods directly on Either
Inherited from:
Either
Source
Either.scala
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Copyright (c) 2002-2025, LAMP/EPFL
Copyright (c) 2002-2025, LAMP/EPFL