Package com.singularsys.jep.walkers

Class 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

      Fields 
      Modifier and Type Field Description
      protected java.util.Stack<java.lang.Object> stack  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object eval​(Node node)
      Evaluates a sub expression.
      java.lang.Object evaluate​(Node node)
      Main entry point, 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 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
        Main entry point, evaluates a node and returns and object with the value of the node.
        Specified by:
        evaluate in interface Evaluator
        Parameters:
        node - node to evaluate
        Returns:
        value after evaluation
        Throws:
        EvaluationException - if errors occur during evaluation;

      • 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.

      • 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 traversal 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. This method can be called by PostfixMathCommands which implement CallbackEvaluationI
        Specified by:
        eval in interface Evaluator
        Parameters:
        node - node to evaluate
        Returns:
        The value after evaluating the sub expression.
        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