final case class Right[+A, +B](value: B) extends Either[A, B] with Product with Serializable
The right side of the disjoint union, as opposed to the scala.util.Left side.
- Source
- Either.scala
- Alphabetic
- By Inheritance
- Right
- Either
- Serializable
- Product
- Equals
- AnyRef
- Any
- by MergeableEither
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
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- Public
- Protected
Instance Constructors
- new Right(value: B)
Value Members
- final def contains[B1 >: B](elem: B1): Boolean
Returns
true
if this is aRight
and its value is equal toelem
(as determined by==
), returnsfalse
otherwise.Returns
true
if this is aRight
and its value is equal toelem
(as determined by==
), returnsfalse
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"
- elem
the element to test.
- returns
true
if this is aRight
value equal toelem
.
- Definition Classes
- Either
- def exists(p: (B) => Boolean): Boolean
Returns
false
ifLeft
or returns the result of the application of the given predicate to theRight
value.Returns
false
ifLeft
or returns the result of the application of the given predicate to theRight
value.Right(12).exists(_ > 10) // true Right(7).exists(_ > 10) // false Left(12).exists(_ => true) // false
- Definition Classes
- Either
- def filterOrElse[A1 >: A](p: (B) => Boolean, zero: => A1): Either[A1, B]
Returns
Right
with the existing value ofRight
if this is aRight
and the given predicatep
holds for the right value, orLeft(zero)
if this is aRight
and the given predicatep
does not hold for the right value, orLeft
with the existing value ofLeft
if this is aLeft
.Returns
Right
with the existing value ofRight
if this is aRight
and the given predicatep
holds for the right value, orLeft(zero)
if this is aRight
and the given predicatep
does not hold for the right value, orLeft
with the existing value ofLeft
if this is aLeft
.Right(12).filterOrElse(_ > 10, -1) // Right(12) Right(7).filterOrElse(_ > 10, -1) // Left(-1) Left(7).filterOrElse(_ => false, -1) // Left(7)
- Definition Classes
- Either
- def flatMap[A1 >: A, B1](f: (B) => Either[A1, B1]): Either[A1, B1]
Binds the given function across
Right
. - 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
- Definition Classes
- Either
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)
Example: - def fold[C](fa: (A) => C, fb: (B) => C): C
Applies
fa
if this is aLeft
orfb
if this is aRight
.Applies
fa
if this is aLeft
orfb
if this is aRight
.- fa
the function to apply if this is a
Left
- fb
the function to apply if this is a
Right
- returns
the results of applying the function
- Definition Classes
- Either
val result = util.Try("42".toInt).toEither result.fold( e => s"Operation failed with $e", v => s"Operation produced value: $v" )
Example: - def forall(f: (B) => Boolean): Boolean
Returns
true
ifLeft
or returns the result of the application of the given predicate to theRight
value.Returns
true
ifLeft
or returns the result of the application of the given predicate to theRight
value.Right(12).forall(_ > 10) // true Right(7).forall(_ > 10) // false Left(12).forall(_ => false) // true
- Definition Classes
- Either
- 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
- f
The side-effecting function to execute.
- Definition Classes
- Either
- def getOrElse[B1 >: B](or: => B1): B1
Returns the value from this
Right
or the given argument if this is aLeft
.Returns the value from this
Right
or the given argument if this is aLeft
.Right(12).getOrElse(17) // 12 Left(12).getOrElse(17) // 17
- Definition Classes
- Either
- def isLeft: Boolean
Returns
true
if this is aLeft
,false
otherwise. - def isRight: Boolean
Returns
true
if this is aRight
,false
otherwise. - def joinLeft[A1 >: A, B1 >: B, C](implicit ev: <:<[A1, Either[C, B1]]): Either[C, B1]
Joins an
Either
throughLeft
.Joins an
Either
throughLeft
.This method requires that the left side of this
Either
is itself anEither
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 containedEither[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 toOption#flatten
.- Definition Classes
- Either
- def joinRight[A1 >: A, B1 >: B, C](implicit ev: <:<[B1, Either[A1, C]]): Either[A1, C]
Joins an
Either
throughRight
.Joins an
Either
throughRight
.This method requires that the right side of this
Either
is itself anEither
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 containedEither[A, C]
will be returned, otherwise this value will be returned unmodified.- Definition Classes
- Either
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 toOption#flatten
Example: - def left: LeftProjection[A, B]
Projects this
Either
as aLeft
.Projects this
Either
as aLeft
.This allows for-comprehensions over the left side of
Either
instances, reversingEither
'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 thatLeft
should be analogous toSome
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")
- Definition Classes
- Either
- 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)
- Definition Classes
- Either
- def merge: B
- Implicit
- This member is added by an implicit conversion from Right[A, B] toMergeableEither[B] performed by method MergeableEither in scala.util.Either.This conversion will take place only if B is a superclass of A (B >: A).
- Definition Classes
- MergeableEither
- def orElse[A1 >: A, B1 >: B](or: => Either[A1, B1]): Either[A1, B1]
Returns this
Right
or the given argument if this is aLeft
.Returns this
Right
or the given argument if this is aLeft
.Right(1) orElse Left(2) // Right(1) Left(1) orElse Left(2) // Left(2) Left(1) orElse Left(2) orElse Right(3) // Right(3)
- Definition Classes
- Either
- 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.
- Definition Classes
- Product
- def swap: Either[B, A]
If this is a
Left
, then return the left value inRight
or vice versa.If this is a
Left
, then return the left value inRight
or vice versa.- Definition Classes
- Either
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)
Examples: - def toOption: Option[B]
Returns a
Some
containing theRight
value if it exists or aNone
if this is aLeft
.Returns a
Some
containing theRight
value if it exists or aNone
if this is aLeft
.Right(12).toOption // Some(12) Left(12).toOption // None
- Definition Classes
- Either
- def toSeq: collection.immutable.Seq[B]
Returns a
Seq
containing theRight
value if it exists or an emptySeq
if this is aLeft
.Returns a
Seq
containing theRight
value if it exists or an emptySeq
if this is aLeft
.Right(12).toSeq // Seq(12) Left(12).toSeq // Seq()
- Definition Classes
- Either
- def toTry(implicit ev: <:<[A, Throwable]): Try[B]
- Definition Classes
- Either
- val value: B
- def withLeft[A1 >: A]: Either[A1, B]
Upcasts this
Right[A, B]
toEither[A1, B]
Upcasts this
Right[A, B]
toEither[A1, B]
Right("x") // Either[Nothing, String] Right("x").withLeft[Int] // Either[Int, String]
Deprecated Value Members
- def right: RightProjection[A, B]
Projects this
Either
as aRight
.Projects this
Either
as aRight
.Because
Either
is right-biased, this method is not normally needed.- Definition Classes
- Either
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Either is now right-biased, use methods directly on Either
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.collection.parallel
- Parallel collections (scala-parallel-collections.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)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 forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.