ptolemy.actor.lib
Class Expression

java.lang.Object
  ptolemy.kernel.util.NamedObj
      ptolemy.kernel.InstantiableNamedObj
          ptolemy.kernel.Entity
              ptolemy.kernel.ComponentEntity
                  ptolemy.actor.AtomicActor
                      ptolemy.actor.TypedAtomicActor
                          ptolemy.actor.lib.Expression

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Actor, Executable, FiringsRecordable, Initializable, TypedActor, Changeable, Debuggable, DebugListener, Derivable, Instantiable, ModelErrorHandler, MoMLExportable, Moveable, Nameable

public class Expression
extends TypedAtomicActor

On each firing, evaluate an expression that may include references to the inputs, current time, and a count of the firing. The ports are referenced by the identifiers that have the same name as the port. To use this class, instantiate it, then add ports (instances of TypedIOPort). In vergil, you can add ports by right clicking on the icon and selecting "Configure Ports". In MoML you can add ports by just including ports of class TypedIOPort, set to be inputs, as in the following example:

 <entity name="exp" class="ptolemy.actor.lib.Expression">
 <port name="in" class="ptolemy.actor.TypedIOPort">
 <property name="input"/>
 </port>
 </entity>
 

This actor is type-polymorphic. The types of the inputs can be arbitrary and the types of the outputs are inferred from the expression based on the types inferred for the inputs.

The expression parameter specifies an expression that can refer to the inputs by name. By default, the expression is empty, and attempting to execute the actor without setting it triggers an exception. This actor can be used instead of many of the arithmetic actors, such as AddSubtract, MultiplyDivide, and TrigFunction. However, those actors will be usually be more efficient, and sometimes more convenient to use.

The expression language understood by this actor is the same as that used to set any parameter value, with the exception that the expressions evaluated by this actor can refer to the values of inputs, and to the current time by the identifier name "time", and to the current iteration count by the identifier named "iteration."

This actor requires its all of its inputs to be present. If inputs are not all present, then an exception will be thrown.

NOTE: There are a number of limitations in the current implementation. Primarily, multiports are not supported.

Since:

Ptolemy II 0.2

Version:

$Id: Expression.java 57040 2010-01-27 20:52:32Z cxh $

Author:

Xiaojun Liu, Edward A. Lee, Steve Neuendorffer

See Also:

Serialized Form

Accepted Rating:

Green (neuendor)

Proposed Rating:

Green (neuendor)

Nested Class Summary

private class	Expression.OutputTypeFunction
private class	Expression.VariableScope

Nested classes/interfaces inherited from class ptolemy.kernel.Entity

Entity.ContainedObjectsIterator

Field Summary

private int	_iterationCount
private ASTPtRootNode	_parseTree
private ParseTreeEvaluator	_parseTreeEvaluator
private Expression.VariableScope	_scope
private java.util.Map	_tokenMap
StringAttribute	expression The expression that is evaluated to produce the output.
TypedIOPort	output The output port.

Fields inherited from class ptolemy.actor.AtomicActor

_actorFiringListeners, _initializables, _notifyingActorFiring, _stopRequested

Fields inherited from class ptolemy.kernel.util.NamedObj

_changeListeners, _changeLock, _changeRequests, _debugging, _debugListeners, _elementName, _isPersistent, _verbose, _workspace, ATTRIBUTES, CLASSNAME, COMPLETE, CONTENTS, DEEP, FULLNAME, LINKS

Fields inherited from interface ptolemy.actor.Executable

COMPLETED, NOT_READY, STOP_ITERATING

Constructor Summary

Expression(CompositeEntity container, java.lang.String name)
Construct an actor with the given container and name.

Method Summary

private void	_setOutputTypeConstraint()
void	attributeChanged(Attribute attribute) React to a change in the value of an attribute.
java.lang.Object	clone(Workspace workspace) Clone the actor into the specified workspace.
void	fire() Evaluate the expression and send its result to the output.
void	initialize() Initialize the iteration count to 1.
boolean	postfire() Increment the iteration count.
boolean	prefire() Prefire this actor.
void	preinitialize() Preinitialize this actor.

Methods inherited from class ptolemy.actor.TypedAtomicActor

_addPort, _fireAt, _fireAt, attributeTypeChanged, clone, newPort, typeConstraintList, typeConstraints

Methods inherited from class ptolemy.actor.AtomicActor

_actorFiring, _actorFiring, addActorFiringListener, addInitializable, connectionsChanged, createReceivers, declareDelayDependency, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, isStrict, iterate, newReceiver, outputPortList, pruneDependencies, recordFiring, removeActorFiringListener, removeDependency, removeInitializable, setContainer, stop, stopFire, terminate, wrapup

Methods inherited from class ptolemy.kernel.ComponentEntity

_adjustDeferrals, _checkContainer, _getContainedObject, _propagateExistence, getContainer, instantiate, isAtomic, isOpaque, moveDown, moveToFirst, moveToIndex, moveToLast, moveUp, propagateExistence, setName

Methods inherited from class ptolemy.kernel.Entity

_description, _exportMoMLContents, _removePort, _validateSettables, connectedPortList, connectedPorts, containedObjectsIterator, getAttribute, getPort, getPorts, linkedRelationList, linkedRelations, portList, removeAllPorts, setClassDefinition, uniqueName

Methods inherited from class ptolemy.kernel.InstantiableNamedObj

_setParent, exportMoML, getChildren, getElementName, getParent, getPrototypeList, isClassDefinition, isWithinClassDefinition

Methods inherited from class ptolemy.kernel.util.NamedObj

_addAttribute, _adjustOverride, _attachText, _cloneFixAttributeFields, _debug, _debug, _debug, _debug, _debug, _getIndentPrefix, _isMoMLSuppressed, _markContentsDerived, _propagateValue, _recordDecoratedAttributes, _removeAttribute, _splitName, _stripNumericSuffix, addChangeListener, addDebugListener, attributeList, attributeList, deepContains, depthInHierarchy, description, description, event, executeChangeRequests, exportMoML, exportMoML, exportMoML, exportMoML, exportMoMLPlain, getAttribute, getAttributes, getChangeListeners, getClassName, getDecoratorAttribute, getDecoratorAttributes, getDerivedLevel, getDerivedList, getDisplayName, getFullName, getModelErrorHandler, getName, getName, getSource, handleModelError, isDeferringChangeRequests, isOverridden, isPersistent, lazyContainedObjectsIterator, message, propagateValue, propagateValues, removeChangeListener, removeDebugListener, requestChange, setClassName, setDeferringChangeRequests, setDerivedLevel, setDisplayName, setModelErrorHandler, setPersistent, setSource, sortContainedObjects, toplevel, toString, validateSettables, workspace

Methods inherited from class java.lang.Object

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

Methods inherited from interface ptolemy.actor.Actor

createReceivers, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortList

Methods inherited from interface ptolemy.actor.Executable

isFireFunctional, isStrict, iterate, stop, stopFire, terminate

Methods inherited from interface ptolemy.actor.Initializable

addInitializable, removeInitializable, wrapup

Methods inherited from interface ptolemy.kernel.util.Nameable

description, getContainer, getDisplayName, getFullName, getName, getName, setName

Methods inherited from interface ptolemy.kernel.util.Derivable

getDerivedLevel, getDerivedList, propagateValue

Field Detail

output

public TypedIOPort output

The output port.

expression

public StringAttribute expression

The expression that is evaluated to produce the output.

_iterationCount

private int _iterationCount

_parseTree

private ASTPtRootNode _parseTree

_parseTreeEvaluator

private ParseTreeEvaluator _parseTreeEvaluator

_scope

private Expression.VariableScope _scope

_tokenMap

private java.util.Map _tokenMap

Constructor Detail

Expression

public Expression(CompositeEntity container,
                  java.lang.String name)
           throws NameDuplicationException,
                  IllegalActionException

Construct an actor with the given container and name.

Parameters:

container - The container.

name - The name of this actor.

Throws:

IllegalActionException - If the actor cannot be contained by the proposed container.

NameDuplicationException - If the container already has an actor with this name.

Method Detail

attributeChanged

public void attributeChanged(Attribute attribute)
                      throws IllegalActionException

React to a change in the value of an attribute.

Overrides:

attributeChanged in class NamedObj

Parameters:

attribute - The attribute whose type changed.

Throws:

IllegalActionException - Not thrown in this base class.

clone

public java.lang.Object clone(Workspace workspace)
                       throws java.lang.CloneNotSupportedException

Clone the actor into the specified workspace. This calls the base class and then creates new ports and parameters.

Overrides:

clone in class AtomicActor

Parameters:

workspace - The workspace for the new object.

Returns:

A new actor.

Throws:

java.lang.CloneNotSupportedException - If a derived class contains an attribute that cannot be cloned.

See Also:

NamedObj.exportMoML(Writer, int, String), NamedObj.setDeferringChangeRequests(boolean)

fire

public void fire()
          throws IllegalActionException

Evaluate the expression and send its result to the output.

Specified by:

fire in interface Executable

Overrides:

fire in class AtomicActor

Throws:

IllegalActionException - If the evaluation of the expression triggers it, or the evaluation yields a null result, or the evaluation yields an incompatible type, or if there is no director, or if a connected input has no tokens.

initialize

public void initialize()
                throws IllegalActionException

Initialize the iteration count to 1.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class AtomicActor

Throws:

IllegalActionException - If the parent class throws it.

postfire

public boolean postfire()
                 throws IllegalActionException

Increment the iteration count.

Specified by:

postfire in interface Executable

Overrides:

postfire in class AtomicActor

Returns:

True if execution can continue into the next iteration.

Throws:

IllegalActionException - If the superclass throws it.

prefire

public boolean prefire()
                throws IllegalActionException

Prefire this actor. Return false if an input port has no data, otherwise return true.

Specified by:

prefire in interface Executable

Overrides:

prefire in class AtomicActor

Returns:

True if this actor is ready for firing, false otherwise.

Throws:

IllegalActionException - If the superclass throws it.

preinitialize

public void preinitialize()
                   throws IllegalActionException

Preinitialize this actor.

Specified by:

preinitialize in interface Initializable

Overrides:

preinitialize in class AtomicActor

Throws:

IllegalActionException - Not thrown in this base class.

_setOutputTypeConstraint

private void _setOutputTypeConstraint()