scala.util.continuations

ControlContext

final class ControlContext[+A, -B, +C] extends Serializable

This class represent a portion of computation that has a 'hole' in it. The class has the ability to compute state up until a certain point where the state has the A type. If this context is given a function of type A => B to move the state to the B type, then the entire computation can be completed resulting in a value of type C.

An Example: 

  val cc = new ControlContext[String, String, String](
     fun = { (f: String=>String, err: Exception => String) =>
       val updatedState =
         try f("State")
         catch {
           case e: Exception => err(e)
         }
       updatedState + "-Complete!"
     },
     x = null.asIntanceOf[String]
 }
 cc.foreach(_ + "-Continued")  // Results in "State-Continued-Complete!"

This class is used to transform calls to shift in the continuations package. Direct use and instantiation is possible, but usually reserved for advanced cases.

A context may either be trivial or non-trivial. A trivial context just has a state of type A. When completing the computation, it's only necessary to use the function of type A => B directly against the trivial value. A non-trivial value stores a computation around the state transformation of type A => B and cannot be short-circuited.

A

The type of the state currently held in the context.

B

The type of the transformed state needed to complete this computation.

C

The return type of the entire computation stored in this context.

Source
ControlContext.scala
Note

fun and x are allowed to be null.

See also

scala.util.continutations.shiftR

Linear Supertypes
Serializable, Serializable, AnyRef, Any
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  1. ControlContext
  2. Serializable
  3. Serializable
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Instance Constructors

  1. new ControlContext(fun: ((A) ⇒ B, (Exception) ⇒ B) ⇒ C, x: A)

    fun

    The captured computation so far. The type (A => B, Exception => B) => C is a function where:

    • The first parameter A=>B represents the computation defined against the current state held in the ControlContext.
    • The second parameter Exception => B represents a computation to perform if an exception is thrown from the first parameter's computation.
    • The return value is the result of the entire computation contained in this ControlContext.
    x

    The current state stored in this context. Allowed to be null if the context is non-trivial.

Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  2. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

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

    Definition Classes
    Any

  3. final def ##(): Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    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
    AnyRef → Any

  4. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  5. final def ==(arg0: Any): Boolean

    Test two objects for equality.

    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

  6. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type 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.

  7. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  8. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef

  9. def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in Any.

    returns

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

    Definition Classes
    AnyRef → Any

  10. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  11. final def flatMap[A1, B1, C1 <: B](f: (A) ⇒ ControlContext[A1, B1, C1]): ControlContext[A1, B1, C]

    Maps and flattens this ControlContext with another ControlContext generated from the current state.

    Maps and flattens this ControlContext with another ControlContext generated from the current state.

    A1

    The new type of the contained state.

    B1

    The new type of the state after the stored continuation has executed.

    C1

    The result type of the nested ControlContext. Because the nested ControlContext is executed within the outer ControlContext, this type must >: B so that the resulting nested computation can be fed through the current continuation.

    f

    A transformation function from the current state to a nested ControlContext.

    returns

    The transformed ControlContext.

    Annotations
    @noinline()
    Note

    The resulting comuptation is still the type C.

  12. final def flatMapCatch[A1 >: A, B1 <: B, C1 >: C <: B1](pf: PartialFunction[Exception, ControlContext[A1, B1, C1]]): ControlContext[A1, B1, C1]

  13. final def foreach(f: (A) ⇒ B): C

    Runs the computation against the state stored in this ControlContext.

    Runs the computation against the state stored in this ControlContext.

    f

    the computation that modifies the current state of the context.

    Note

    This method could throw exceptions from the computations.

  14. def foreachFull(f: (A) ⇒ B, g: (Exception) ⇒ B): C

  15. val fun: ((A) ⇒ B, (Exception) ⇒ B) ⇒ C

    The captured computation so far.

    The captured computation so far. The type (A => B, Exception => B) => C is a function where:

    • The first parameter A=>B represents the computation defined against the current state held in the ControlContext.
    • The second parameter Exception => B represents a computation to perform if an exception is thrown from the first parameter's computation.
    • The return value is the result of the entire computation contained in this ControlContext.

  16. final def getClass(): Class[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

    a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
    AnyRef → Any
    Note

    not specified by SLS as a member of AnyRef

  17. final def getTrivialValue: A

    returns

    The current state value.

  18. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any

  19. final def isInstanceOf[T0]: Boolean

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

    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

  20. final def isTrivial: Boolean

    returns

    true if this context only stores a state value and not any deferred computation.

  21. final def map[A1](f: (A) ⇒ A1): ControlContext[A1, B, C]

    Modifies the currently captured state in this ControlContext.

    Modifies the currently captured state in this ControlContext.

    A1

    The new type of state in this context.

    f

    A transformation function on the current state of the ControlContext.

    returns

    The new ControlContext.

    Annotations
    @noinline()

  22. final def mapFinally(f: () ⇒ Unit): ControlContext[A, B, C]

  23. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef

  24. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  25. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  26. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef

  27. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    AnyRef → Any

  28. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

  29. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

  30. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

  31. val x: A

    The current state stored in this context.

    The current state stored in this context. Allowed to be null if the context is non-trivial.

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any