ptolemy.domains.fsm.kernel
Class ParseTreeEvaluatorForGuardExpression

java.lang.Object
  ptolemy.data.expr.AbstractParseTreeVisitor
      ptolemy.data.expr.ParseTreeEvaluator
          ptolemy.domains.fsm.kernel.ParseTreeEvaluatorForGuardExpression

All Implemented Interfaces:

ParseTreeVisitor

public class ParseTreeEvaluatorForGuardExpression
extends ParseTreeEvaluator

This class extends the ParseTreeEvaluator class. It is specially designed for guard expressions associated with transitions of FSM. An object of this class is a visitor that visits a parse tree of a guard expression and evaluates it into a token. Meanwhile, this visitor stores the type and difference of all relations of the guard expression into a relation list. Here a relation means an expression that does not contain a logical operator.

This visitor has two modes of operation: construction mode and update mode. During the construction mode, this visitor constructs a relation list where each element of the list corresponds to a relation of the guard expression. The order of the elements is fixed and it is the same as the order that the relations appear in the guard expression. If the guard expression changes, the relation list will be reconstructed. During the update mode, the relation list gets updated only. The order of the elements get updated is the same order the relations of the guard expression get evaluated.

When this visitor evaluates the parse tree, if the visiting node is a leaf node and the evaluated token is a boolean token, or the visiting node is a relational node, the visiting node is treated as a relation. The visitor evaluates the 'difference' and 'relationType' of this relation, and stores the evaluation results into the corresponding element in the relation list.

The 'difference' of a relation is calculated in the following way. For a leaf node evaluated as a boolean token, the difference is 0. This situation corresponds to the "true", or "false", or "x_isPresent" elements in a guard expression. For a relational node with the format (scalarLeft relationOperator scalarRight), the difference is the absolute double value of (scalarLeft - scalarRight). For details of relation type, see RelationType.

If the evaluator is in the construction mode, the relation information is added into the relation list, if it is in the update mode, the corresponding element of the relation List gets updated.

Note, this evaluator does not use short-circuit evaluation on logical nodes, meaning all nodes will be evaluated.

Since:

Ptolemy II 4.0

Version:

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

Author:

Haiyang Zheng

See Also:

RelationList, ParseTreeEvaluator

Accepted Rating:

Red (hyzheng)

Proposed Rating:

Red (hyzheng)

Field Summary

private java.util.LinkedList<java.lang.String>	_absentDiscreteVariables
private boolean	_constructingRelationList
private double	_difference
private double	_errorTolerance
private int	_relationIndex
private RelationList	_relationList
private int	_relationType
private ParseTreeFreeVariableCollector	_variableCollector

Fields inherited from class ptolemy.data.expr.ParseTreeEvaluator

_evaluatedChildToken, _typeInference

Constructor Summary

ParseTreeEvaluatorForGuardExpression(RelationList relationList, double errorTolerance)
Construct a parse tree evaluator for a guard expression of the given relation list and the error tolerance for evaluation the relations.

Method Summary

Token	evaluateParseTree(ASTPtRootNode node, ParserScope scope) Evaluate the parse tree with the specified root node using the specified scope to resolve the values of variables.
RelationList	getRelationList() Return the list of relations (boolean-valued expressions that do not contain a logical operator, such as comparison expressions) in the guard expression of this transition.
void	setConstructionMode() Set parse tree evaluator to be in construction mode.
void	visitLeafNode(ASTPtLeafNode node) Visit the leaf node.
void	visitLogicalNode(ASTPtLogicalNode node) Visit the logical node.
void	visitRelationalNode(ASTPtRelationalNode node) Visit the relation node.

Methods inherited from class ptolemy.data.expr.ParseTreeEvaluator

_assert, _evaluateAllChildren, _evaluateArrayIndex, _evaluateChild, _evaluateMatrixIndex, _functionCall, _methodCall, _trace, _traceEnter, _traceLeave, evaluateParseTree, traceParseTreeEvaluation, visitArrayConstructNode, visitBitwiseNode, visitFunctionalIfNode, visitFunctionApplicationNode, visitFunctionDefinitionNode, visitMatrixConstructNode, visitMethodCallNode, visitPowerNode, visitProductNode, visitRecordConstructNode, visitShiftNode, visitSumNode, visitUnaryNode, visitUnionConstructNode

Methods inherited from class ptolemy.data.expr.AbstractParseTreeVisitor

_unsupportedVisitException, _visitAllChildren, _visitChild, visitAssignmentNode

Methods inherited from class java.lang.Object

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

Field Detail

_absentDiscreteVariables

private java.util.LinkedList<java.lang.String> _absentDiscreteVariables

_constructingRelationList

private boolean _constructingRelationList

_difference

private double _difference

_errorTolerance

private double _errorTolerance

_relationIndex

private int _relationIndex

_relationList

private RelationList _relationList

_relationType

private int _relationType

_variableCollector

private ParseTreeFreeVariableCollector _variableCollector

Constructor Detail

ParseTreeEvaluatorForGuardExpression

public ParseTreeEvaluatorForGuardExpression(RelationList relationList,
                                            double errorTolerance)

Construct a parse tree evaluator for a guard expression of the given relation list and the error tolerance for evaluation the relations. The relation stores the information of the relation. After the parse tree evaluator is created, it is always in construction mode.

Parameters:

relationList - The relation list.

errorTolerance - The errorTolerance.

Method Detail

evaluateParseTree

public Token evaluateParseTree(ASTPtRootNode node,
                               ParserScope scope)
                        throws IllegalActionException

Evaluate the parse tree with the specified root node using the specified scope to resolve the values of variables.

Overrides:

evaluateParseTree in class ParseTreeEvaluator

Parameters:

node - The root of the parse tree.

scope - The scope for evaluation.

Returns:

The result of evaluation.

Throws:

IllegalActionException - If an error occurs during evaluation.

getRelationList

public RelationList getRelationList()

Return the list of relations (boolean-valued expressions that do not contain a logical operator, such as comparison expressions) in the guard expression of this transition.

Returns:

The list of relations.

setConstructionMode

public void setConstructionMode()

Set parse tree evaluator to be in construction mode. Clear the relation list and the relation list will be populated, based on the nodes in the parse tree.

visitLeafNode

public void visitLeafNode(ASTPtLeafNode node)
                   throws IllegalActionException

Visit the leaf node. It is evaluated the same way as normal parse tree evaluator, except that if the the result is a boolean token, the information about the node (the difference and relationType) is either added into the relation list or used to update the corresponding element in the relation list, depending on the evaluator mode.

Specified by:

visitLeafNode in interface ParseTreeVisitor

Overrides:

visitLeafNode in class ParseTreeEvaluator

Parameters:

node - The leaf node to be evaluated.

Throws:

IllegalActionException - If the super class method visitLeafNode throws the IllegalActionException.

visitLogicalNode

public void visitLogicalNode(ASTPtLogicalNode node)
                      throws IllegalActionException

Visit the logical node. This visitor does not use short-circuit evaluation. It evaluates both the nodes beside the logical operator.

Specified by:

visitLogicalNode in interface ParseTreeVisitor

Overrides:

visitLogicalNode in class ParseTreeEvaluator

Parameters:

node - The logical node to be evaluated.

Throws:

IllegalActionException - If the super class method visitLogicalNode throws the IllegalActionException.

visitRelationalNode

public void visitRelationalNode(ASTPtRelationalNode node)
                         throws IllegalActionException

Visit the relation node. The evaluation part is the same as normal parseTreeEvaluator, except that information about each relation (the difference and relationType) is either added into the relation list or used to update the corresponding element in the relation list, depending on the evaluator mode.

Specified by:

visitRelationalNode in interface ParseTreeVisitor

Overrides:

visitRelationalNode in class ParseTreeEvaluator

Parameters:

node - The relation node to be evaluated.

Throws:

IllegalActionException - If the super class method visitRelationNode throws the IllegalActionException.