Packages

sealed abstract class \/[A, B] extends Product with Serializable

Represents a disjunction: a result that is either an A or a B.

An instance of A \/ B is either a -\/[A] (aka a "left") or a \/-[B] (aka a "right").

A common use of a disjunction is to explicitly represent the possibility of failure in a result as opposed to throwing an exception. By convention, the left is used for errors and the right is reserved for successes. For example, a function that attempts to parse an integer from a string may have a return type of NumberFormatException \/ Int. However, since there is no need to actually throw an exception, the type (A) chosen for the "left" could be any type representing an error and has no need to actually extend Exception.

A \/ B is isomorphic to scala.Either[A, B], but \/ is right-biased for all Scala versions, so methods such as map and flatMap apply only in the context of the "right" case. This right bias makes \/ more convenient to use than scala.Either in a monadic context in Scala versions <2.12. Methods such as swap, swapped, and leftMap provide functionality that scala.Either exposes through left projections.

A \/ B is also isomorphic to Validation[A, B]. The subtle but important difference is that Applicative instances for Validation accumulates errors ("lefts") while Applicative instances for \/ fail fast on the first "left" they evaluate. This fail-fast behavior allows \/ to have lawful Monad instances that are consistent with their Applicative instances, while Validation cannot.

Source
Either.scala
Linear Supertypes
Serializable, Serializable, Product, Equals, AnyRef, Any
Known Subclasses
-\/, \/-
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. \/
  2. Serializable
  3. Serializable
  4. Product
  5. Equals
  6. AnyRef
  7. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. All

Type Members

  1. final class SwitchingDisjunction[X] extends AnyRef

Abstract Value Members

  1. abstract def canEqual(that: Any): Boolean
    Definition Classes
    Equals
  2. abstract def productArity: Int
    Definition Classes
    Product
  3. abstract def productElement(n: Int): Any
    Definition Classes
    Product

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. def +++(x: ⇒ \/[A, B])(implicit M1: Semigroup[B], M2: Semigroup[A]): \/[A, B]

    Sums up values inside disjunction, if both are left or right.

    Sums up values inside disjunction, if both are left or right. Returns first left otherwise.

    \/-(v1) +++ \/-(v2) → \/-(v1 + v2)
\/-(v1) +++ -\/(v2) → -\/(v2)
-\/(v1) +++ \/-(v2) → -\/(v1)
-\/(v1) +++ -\/(v2) → -\/(v1 + v2)
  4. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  5. def ===[AA >: A, BB >: B](x: \/[AA, BB])(implicit EA: Equal[AA], EB: Equal[BB]): Boolean

    Compare two disjunction values for equality.

  6. def @\?/[AA, BB](k: (Validation[A, B]) ⇒ Validation[AA, BB]): \/[AA, BB]

    Run a validation function and back to disjunction again.

    Run a validation function and back to disjunction again. Alias for validationed

  7. def ap[C](f: ⇒ \/[A, (B) ⇒ C]): \/[A, C]

    Apply a function in the environment of the right of this disjunction.

  8. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  9. def bimap[C, D](f: (A) ⇒ C, g: (B) ⇒ D): \/[C, D]

    Binary functor map on this disjunction.

  10. def bitraverse[F[_], C, D](f: (A) ⇒ F[C], g: (B) ⇒ F[D])(implicit arg0: Functor[F]): F[\/[C, D]]

    Binary functor traverse on this disjunction.

  11. def clone(): AnyRef
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  12. def compare[AA >: A, BB >: B](x: \/[AA, BB])(implicit EA: Order[AA], EB: Order[BB]): Ordering

    Compare two disjunction values for ordering.

  13. def ensure(onLeft: ⇒ A)(f: (B) ⇒ Boolean): \/[A, B]

    Ensures that the right value of this disjunction satisfies the given predicate, or returns left with the given value.

  14. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  15. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  16. def exists[BB >: B](p: (BB) ⇒ Boolean): Boolean

    Return true if this disjunction is a right value satisfying the given predicate.

  17. def filter(p: (B) ⇒ Boolean)(implicit M: Monoid[A]): \/[A, B]

    Filter on the right of this disjunction.

  18. def finalize(): Unit
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  19. def flatMap[D](g: (B) ⇒ \/[A, D]): \/[A, D]

    Bind through the right of this disjunction.

  20. def fold[X](l: (A) ⇒ X, r: (B) ⇒ X): X

    Catamorphism.

    Catamorphism. Run the first given function if left, otherwise, the second given function.

  21. def foldConst[X](l: ⇒ X, r: ⇒ X): X

    Evaluate l and return if left, otherwise, r.

  22. def foldRight[Z](z: ⇒ Z)(f: (B, ⇒ Z) ⇒ Z): Z

    Fold on the right of this disjunction.

  23. def forall[BB >: B](p: (BB) ⇒ Boolean): Boolean

    Return true if this disjunction is a left value or the right value satisfies the given predicate.

  24. def foreach(g: (B) ⇒ Unit): Unit

    Run the side-effect on the right of this disjunction.

  25. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  26. def getOrElse[BB >: B](x: ⇒ BB): BB

    Return the right value of this disjunction or the given default if left.

    Return the right value of this disjunction or the given default if left. Alias for |

  27. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  28. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  29. def isLeft: Boolean

    Return true if this disjunction is left.

  30. def isRight: Boolean

    Return true if this disjunction is right.

  31. def leftMap[C](f: (A) ⇒ C): \/[C, B]

    Run the given function on the left value.

  32. def loopl[X](left: (A) ⇒ \/[X, \/[A, B]], right: (B) ⇒ X): X

    Spin in tail-position on the left value of this disjunction.

  33. def loopr[X](left: (A) ⇒ X, right: (B) ⇒ \/[X, \/[A, B]]): X

    Spin in tail-position on the right value of this disjunction.

  34. def map[D](g: (B) ⇒ D): \/[A, D]

    Map on the right of this disjunction.

  35. def merge[AA >: A](implicit ev: <~<[B, AA]): AA

    Return the value from whichever side of the disjunction is defined, given a commonly assignable type.

  36. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  37. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  38. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  39. def orElse[C](x: ⇒ \/[C, B]): \/[C, B]

    Return this if it is a right, otherwise, return the given value.

    Return this if it is a right, otherwise, return the given value. Alias for |||

  40. def orRaiseError[F[_]](implicit F: MonadError[F, A]): F[B]
  41. def productIterator: Iterator[Any]
    Definition Classes
    Product
  42. def productPrefix: String
    Definition Classes
    Product
  43. def recover(pf: PartialFunction[A, B]): \/[A, B]

    Run the given function on the left and return right with the result.

  44. def recoverWith(pf: PartialFunction[A, \/[A, B]]): \/[A, B]

    Run the given function on the left and return the result.

  45. def show[AA >: A, BB >: B](implicit SA: Show[AA], SB: Show[BB]): Cord

    Show for a disjunction value.

  46. def swap: \/[B, A]

    Flip the left/right values in this disjunction.

    Flip the left/right values in this disjunction. Alias for unary_~

  47. def swapped[AA, BB](k: (\/[B, A]) ⇒ \/[BB, AA]): \/[AA, BB]

    Run the given function on this swapped value.

    Run the given function on this swapped value. Alias for ~

  48. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  49. def toEither: Either[A, B]

    Convert to a core scala.Either at your own peril.

  50. def toIList[BB >: B]: IList[BB]

    Return an empty list or list with one element on the right of this disjunction.

  51. def toList: List[B]

    Return an empty list or list with one element on the right of this disjunction.

  52. def toMaybe[BB >: B]: Maybe[BB]

    Return an empty maybe or option with one element on the right of this disjunction.

    Return an empty maybe or option with one element on the right of this disjunction. Useful to sweep errors under the carpet.

  53. def toOption: Option[B]

    Return an empty option or option with one element on the right of this disjunction.

    Return an empty option or option with one element on the right of this disjunction. Useful to sweep errors under the carpet.

  54. def toStream: Stream[B]

    Return an empty stream or stream with one element on the right of this disjunction.

  55. def toString(): String
    Definition Classes
    AnyRef → Any
  56. def toThese: \&/[A, B]

    Convert to a These.

  57. def traverse[F[_], D](g: (B) ⇒ F[D])(implicit arg0: Applicative[F]): F[\/[A, D]]

    Traverse on the right of this disjunction.

  58. def unary_~: \/[B, A]

    Flip the left/right values in this disjunction.

    Flip the left/right values in this disjunction. Alias for swap

  59. def validation: Validation[A, B]

    Convert to a Validation.

  60. def validationNel[AA >: A]: ValidationNel[AA, B]

    Convert to a ValidationNel.

  61. def validationed[AA, BB](k: (Validation[A, B]) ⇒ Validation[AA, BB]): \/[AA, BB]

    Run a validation function and back to disjunction again.

    Run a validation function and back to disjunction again. Alias for @\?/

  62. def valueOr[BB >: B](x: (A) ⇒ BB): BB

    Return the right value of this disjunction or run the given function on the left.

  63. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  64. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  65. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  66. def |[BB >: B](x: ⇒ BB): BB

    Return the right value of this disjunction or the given default if left.

    Return the right value of this disjunction or the given default if left. Alias for getOrElse

  67. def |||[C](x: ⇒ \/[C, B]): \/[C, B]

    Return this if it is a right, otherwise, return the given value.

    Return this if it is a right, otherwise, return the given value. Alias for orElse

  68. def ~[AA, BB](k: (\/[B, A]) ⇒ \/[BB, AA]): \/[AA, BB]

    Run the given function on this swapped value.

    Run the given function on this swapped value. Alias for swapped

Deprecated Value Members

  1. def :?>>[X](right: ⇒ X): SwitchingDisjunction[X]

    If this disjunction is right, return the given X value, otherwise, return the X value given to the return value.

    If this disjunction is right, return the given X value, otherwise, return the X value given to the return value.

    Annotations
    @deprecated
    Deprecated

    (Since version 7.3.0) Due to SI-1980, <<?: will always evaluate its left argument; use foldConst instead

Inherited from Serializable

Inherited from Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

Ungrouped