org.erights.e.elang.interp
Class LazyEvalSlot

java.lang.Object
  |
  +--org.erights.e.elang.interp.LazyEvalSlot

All Implemented Interfaces:

Slot

public class LazyEvalSlot

extends Object

implements Slot

Untamed: Exists to allow delaying the work of really importing during ScopeSetup, while also allowing the imported things to be in the scope they are defining.

For example, rx__quasiParser is in the safe scope, but is obtained lazily from . For this import to work, it needs to provide the safe scope to the evaluation of this module. Laziness allows the safe scope to effectively include things that can't be defined until the safe scope exists.

Must be made thread-safe for the same reasons as org.erights.e.elib.serial.Loader.

Author:

Mark S. Miller

Field Summary

private Object	myLock
private Object	myOptScope only meaningful when myOptSource != null
private Twine	myOptSource to be evaluated in myOptScope
private Object	myOptValue only meaningful when myOptSource == null

Constructor Summary

(package private)

LazyEvalSlot(Object scope, Twine source)

Method Summary

void	__printOn(TextWriter out) Enabled:
Object	getValue() Enabled: Returns the result of evaluating my source text in my scope.
void	setValue(Object newValue) Enabled: Complains that the variable is immutable

Methods inherited from class java.lang.Object

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

Field Detail

myLock

private final Object myLock

myOptScope

private Object myOptScope

only meaningful when myOptSource != null

myOptSource

private Twine myOptSource

to be evaluated in myOptScope

myOptValue

private Object myOptValue

only meaningful when myOptSource == null

Constructor Detail

LazyEvalSlot

LazyEvalSlot(Object scope,
             Twine source)

Parameters:

scope - The scope in which to evaluate the source text. It's declared as an Object rather than Scope so that it can be a promise for a Scope. This promise must become fulfilled before the first getValue() happens.

source - The source text to be evaluated in the promised scope at the time of the first getValue().

Method Detail

getValue

public Object getValue()

Enabled: Returns the result of evaluating my source text in my scope.

This evaluation only happens the first time, after which the value is cached and returned for later requests. If the value isn't DeepPassByCopy, this has security implications, so be careful how you use this class!

Specified by:

getValue in interface Slot

setValue

public void setValue(Object newValue)

Enabled: Complains that the variable is immutable

Specified by:

setValue in interface Slot

__printOn

public void __printOn(TextWriter out)
               throws IOException

Enabled:

IOException