edu.rice.cs.plt.recur
Class PendingContinuation<T>

java.lang.Object
  edu.rice.cs.plt.recur.PendingContinuation<T>

All Implemented Interfaces:

ResolvingThunk<T>, Thunk<T>, Continuation<T>

Direct Known Subclasses:

ArgContinuation, BinaryArgContinuation, ComposedContinuation

public abstract class PendingContinuation<T>
extends Object
implements Continuation<T>

A continuation representing computation left to be done (in contrast to ValueContinuation, which represents a completed computation). This class provides default implementations of value(), isResolved(), and compose(edu.rice.cs.plt.lambda.Lambda>). Subclasses may be defined in one of two ways:

• Simple tail calls may be represented by simply defining an anonymous subclass of PendingContinuation, where the step() method wraps the delayed recursive invocation.
• More complex cases may be handled by defining continuation classes that extend PendingContinuation. ComposedContinuation is one example.

Constructor Summary

PendingContinuation()

Method Summary

<R> Continuation<R>	compose(Lambda<? super T,? extends Continuation<? extends R>> c) Create a ComposedContinuation in terms of this object and the provided function.
boolean	isResolved() Return false.
abstract Continuation<? extends T>	step() Defines the next step of the continuation.
T	value() Iteratively invoke step() until a resolved continuation is produced.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PendingContinuation

public PendingContinuation()

Method Detail

value

public T value()

Iteratively invoke step() until a resolved continuation is produced.

Specified by:

value in interface Thunk<T>

Specified by:

value in interface Continuation<T>

isResolved

public boolean isResolved()

Return false.

Specified by:

isResolved in interface ResolvingThunk<T>

Specified by:

isResolved in interface Continuation<T>

compose

public <R> Continuation<R> compose(Lambda<? super T,? extends Continuation<? extends R>> c)

Create a ComposedContinuation in terms of this object and the provided function.

Specified by:

compose in interface Continuation<T>

step

public abstract Continuation<? extends T> step()

Defines the next step of the continuation. For simple tail calls, this is generally a recursive invocation of the current method (or a related method).

Specified by:

step in interface Continuation<T>