com.singularsys.jep.walkers
Class PostfixEvaluator

java.lang.Object
  com.singularsys.jep.walkers.PostfixTreeWalker
      com.singularsys.jep.walkers.PostfixEvaluator

All Implemented Interfaces:

Evaluator, JepComponent, java.io.Serializable

public class PostfixEvaluator
extends PostfixTreeWalker
implements Evaluator

Evaluation component that avoids excessive use of the stack for large expressions. Instead of using recursion to traverse the expression tree, traversal is based on the PostfixTreeWalker.

Author:

Richard Morris

See Also:

Serialized Form

Field Summary

protected java.util.Stack<java.lang.Object>

stack

Constructor Summary

PostfixEvaluator()

Method Summary

java.lang.Object	eval(Node node) Evaluates a sub expression.
java.lang.Object	evaluate(Node node) Evaluates a node and returns and object with the value of the node.
JepComponent	getLightWeightInstance() Return new PostfixEvaluator
void	init(Jep jep) Initialize the component.
protected boolean	supressExaminingChildren(Node child) Whether to examine the children of this nodes.
protected void	visit(ASTConstant node, int nchildren, int depth) Visit a constant node
protected void	visit(ASTFunNode node, int nchildren, int depth) Visit a function node
protected void	visit(ASTOpNode node, int nchildren, int depth) Visit an operator node
protected void	visit(ASTVarNode node, int nchildren, int depth) Visit a variable node

Methods inherited from class com.singularsys.jep.walkers.PostfixTreeWalker

walk, walkSubEquations

Methods inherited from class java.lang.Object

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

Field Detail

stack

protected transient java.util.Stack<java.lang.Object> stack

Constructor Detail

PostfixEvaluator

public PostfixEvaluator()

Method Detail

evaluate

public java.lang.Object evaluate(Node node)
                          throws EvaluationException

Description copied from interface: Evaluator

Evaluates a node and returns and object with the value of the node.

Specified by:

evaluate in interface Evaluator

Throws:

EvaluationException - if errors occur during evaluation;

visit

protected void visit(ASTFunNode node,
                     int nchildren,
                     int depth)
              throws EvaluationException

Description copied from class: PostfixTreeWalker

Visit a function node

Specified by:

visit in class PostfixTreeWalker

Parameters:

node - the current node being visited

nchildren - number of children of the node

depth - depth of tree, root node is depth 1.

Throws:

EvaluationException

visit

protected void visit(ASTOpNode node,
                     int nchildren,
                     int depth)
              throws EvaluationException

Description copied from class: PostfixTreeWalker

Visit an operator node

Specified by:

visit in class PostfixTreeWalker

Parameters:

node - the current node being visited

nchildren - number of children of the node

depth - depth of tree, root node is depth 1.

Throws:

EvaluationException

visit

protected void visit(ASTVarNode node,
                     int nchildren,
                     int depth)

Description copied from class: PostfixTreeWalker

Visit a variable node

Specified by:

visit in class PostfixTreeWalker

Parameters:

node - the current node being visited

nchildren - number of children of the node

depth - depth of tree, root node is depth 1.

visit

protected void visit(ASTConstant node,
                     int nchildren,
                     int depth)
              throws EvaluationException

Description copied from class: PostfixTreeWalker

Visit a constant node

Specified by:

visit in class PostfixTreeWalker

Parameters:

node - the current node being visited

nchildren - number of children of the node

depth - depth of tree, root node is depth 1.

Throws:

EvaluationException

supressExaminingChildren

protected boolean supressExaminingChildren(Node child)

Description copied from class: PostfixTreeWalker

Whether to examine the children of this nodes. In some cases it is necessary to jump out of transversal strategy to process a node.

Overrides:

supressExaminingChildren in class PostfixTreeWalker

Returns:

false unless overridden by sub-class

eval

public java.lang.Object eval(Node node)
                      throws EvaluationException

Description copied from interface: Evaluator

Evaluates a sub expression.

Specified by:

eval in interface Evaluator

Throws:

EvaluationException - if errors occur during evaluation;

init

public void init(Jep jep)

Description copied from interface: JepComponent

Initialize the component. This methods is called whenever a component is added to Jep. Hence it allows components to keep track of the other components they may rely on.

Specified by:

init in interface JepComponent

Parameters:

jep - the current Jep instance

getLightWeightInstance

public JepComponent getLightWeightInstance()

Return new PostfixEvaluator

Specified by:

getLightWeightInstance in interface JepComponent

Returns:

either an new instance, or 'this'.