Class scala.ValueOf

final class ValueOf[T] extends AnyVal

ValueOf[T] provides the unique value of the type T where T is a type which has a single inhabitant. Eligible types are singleton types of the form stablePath.type, Unit and singleton types corresponding to value literals.

Instances of ValueOf[T] are provided implicitly for all eligible types. Typically an instance would be required where a runtime value corresponding to a type level computation is needed.

For example, we might define a type Residue[M <: Int] corresponding to the group of integers modulo M. We could then mandate that residues can be summed only when they are parameterized by the same modulus,

case class Residue[M <: Int](n: Int) extends AnyVal {
  def +(rhs: Residue[M])(implicit m: ValueOf[M]): Residue[M] =
    Residue((this.n + rhs.n) % valueOf[M])
}

val fiveModTen = Residue[10](5)
val nineModTen = Residue[10](9)

fiveModTen + nineModTen    // OK == Residue[10](4)

val fourModEleven = Residue[11](4)

fiveModTen + fourModEleven // compiler error: type mismatch;
                           //   found   : Residue[11]
                           //   required: Residue[10]

Notice that here the modulus is encoded in the type of the values and so does not incur any additional per-value storage cost. When a runtime value of the modulus is required in the implementation of + it is provided at the call site via the implicit argument m of type ValueOf[M].

Annotations: @implicitNotFound("No singleton value available for ${T}.")
Source: ValueOf.scala
Linear Supertypes: AnyVal, Any

Instance Constructors

new ValueOf(value: T)

Value Members

final def !=(arg0: Any): Boolean

Test two objects for inequality.

returns: true if !(this == that), false otherwise.

Definition Classes: Any

final def ##(): Int

Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

returns: a hash value consistent with ==

Definition Classes: Any

def +(other: String): String

Implicit: This member is added by an implicit conversion from ValueOf[T] toany2stringadd[ValueOf[T]] performed by method any2stringadd in scala.Predef.
Definition Classes: any2stringadd

def ->[B](y: B): (ValueOf[T], B)

Implicit: This member is added by an implicit conversion from ValueOf[T] toArrowAssoc[ValueOf[T]] performed by method ArrowAssoc in scala.Predef.
Definition Classes: ArrowAssoc
Annotations: @inline()

final def ==(arg0: Any): Boolean

Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

returns: true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes: Any

final def asInstanceOf[T0]: T0

Cast the receiver object to be of type T0.

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

returns: the receiver object.

Definition Classes: Any
Exceptions thrown: ClassCastException if the receiver object is not an instance of the erasure of type T0.

def ensuring(cond: (ValueOf[T]) => Boolean, msg: => Any): ValueOf[T]

Implicit: This member is added by an implicit conversion from ValueOf[T] toEnsuring[ValueOf[T]] performed by method Ensuring in scala.Predef.
Definition Classes: Ensuring

def ensuring(cond: (ValueOf[T]) => Boolean): ValueOf[T]

Implicit: This member is added by an implicit conversion from ValueOf[T] toEnsuring[ValueOf[T]] performed by method Ensuring in scala.Predef.
Definition Classes: Ensuring

def ensuring(cond: Boolean, msg: => Any): ValueOf[T]

Implicit: This member is added by an implicit conversion from ValueOf[T] toEnsuring[ValueOf[T]] performed by method Ensuring in scala.Predef.
Definition Classes: Ensuring

def ensuring(cond: Boolean): ValueOf[T]

Implicit: This member is added by an implicit conversion from ValueOf[T] toEnsuring[ValueOf[T]] performed by method Ensuring in scala.Predef.
Definition Classes: Ensuring

def formatted(fmtstr: String): String

Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

Implicit: This member is added by an implicit conversion from ValueOf[T] toStringFormat[ValueOf[T]] performed by method StringFormat in scala.Predef.
Definition Classes: StringFormat
Annotations: @inline()

def getClass(): Class[_ <: AnyVal]

Returns the runtime class representation of the object.

returns: a class object corresponding to the runtime type of the receiver.

Definition Classes: AnyVal → Any

final def isInstanceOf[T0]: Boolean

Test whether the dynamic type of the receiver object is T0.

Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

returns: true if the receiver object is an instance of erasure of type T0; false otherwise.

Definition Classes: Any

def toString(): String

Returns a string representation of the object.

The default representation is platform dependent.

returns: a string representation of the object.

Definition Classes: Any

val value: T

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala/ValueOf.html