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
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
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]
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"
the element to test.
true if this is a Right value equal to elem.
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
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)
Binds the given function across Right.
Binds the given function across Right.
The function to bind across Right.
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
Attributesval 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)
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.
the function to apply if this is a Left
the function to apply if this is a Right
the results of applying the function
val result = util.Try("42".toInt).toEither
result.fold(
e => s"Operation failed with $e",
v => s"Operation produced value: $v"
)
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
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
The side-effecting function to execute.
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
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:
(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.
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:
(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.
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
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")
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)
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)
An iterator over the names of all the elements of this product.
An iterator over the names of all the elements of this product.
AttributesAn iterator over all the elements of this product.
An iterator over all the elements of this product.
Attributesin the default implementation, an Iterator[Any]
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.
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)
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
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()
Projects this Either as a Right.
Projects this Either as a Right.
Because Either is right-biased, this method is not normally needed.
[Since version 2.13.0] Either is now right-biased, use methods directly on Either
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