Left
The left side of the disjoint union, as opposed to the scala.util.Right side.
Attributes
- Source
- Either.scala
- Graph
-
- Supertypes
Members list
Value members
Concrete methods
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
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
Upcasts this Left[A, B] to Either[A, B1]
Upcasts this Left[A, B] to Either[A, B1]
Left(1) // Either[Int, Nothing]
Left(1).withRight[String] // Either[Int, String]
Attributes
- Source
- Either.scala
Inherited methods
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
-
trueif this is aRightvalue equal toelem. - Inherited from:
- Either
- Source
- Either.scala
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
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
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
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
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
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
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
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
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
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 toOption#flatten - Inherited from:
- Either
- Source
- Either.scala
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
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
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
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
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
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
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
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
Deprecated and Inherited methods
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
- true
- Inherited from:
- Either
- Source
- Either.scala