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## com.singularsys.jep.walkers
Class PostfixTreeWalker

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

Direct Known Subclasses:
  PostfixEvaluator, SerializableExpression, TreeAnalyzer

    public abstract class PostfixTreeWalker

extends java.lang.Object

Base class for routines which use a non recursive tree walker strategy. The typical recursive strategy can use a lot of stack frames for very large expressions these can cause a stack overflow exception. Subclasses should implement the visit methods. to transverse the various nodes. In general these methods should not recursively walk the child nodes. This class uses a postfix transversal scheme hence the nodes of '1+2' will be visited in the order 1,2,+.

Since:
  3.2 depth of root node is now 1 not 0
Author:
  Richard Morris
See Also:
  `PrefixTreeWalker`

Constructor Summary
`PostfixTreeWalker()`

Method Summary
`protected boolean` | `supressExaminingChildren(Node child)` Whether to examine the children of this nodes.
`protected abstract void` | `visit(ASTConstant node, int nchildren, int depth)` Visit a constant node
`protected abstract void` | `visit(ASTFunNode node, int nchildren, int depth)` Visit a function node
`protected abstract void` | `visit(ASTOpNode node, int nchildren, int depth)` Visit an operator node
`protected abstract void` | `visit(ASTVarNode node, int nchildren, int depth)` Visit a variable node
`protected void` | `walk(Node top)` Start transversal of the expression.
`protected void` | `walkSubEquations(Node top)` If a supressExaminingChildren() returns true, then the children of the node will not be visited by default.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### PostfixTreeWalker

    public PostfixTreeWalker()

Method Detail

### walk

    protected final void walk(Node top)
                       throws JepException

  Start transversal of the expression.

  Parameters:
    `top` - top node for the expression
  Throws:
    `JepException`

### supressExaminingChildren

    protected boolean supressExaminingChildren(Node child)

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

  Parameters:
    `child` -
  Returns:
    false unless overridden by sub-class

### walkSubEquations

    protected final void walkSubEquations(Node top)
                                   throws JepException

  If a supressExaminingChildren() returns true, then the children of the node will not be visited by default. This method allows a sub-class to visit the children of such a node if needed.

  Parameters:
    `top` -
  Throws:
    `JepException`

### visit

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

  Visit a function node

  Parameters:
    `node` - the current node being visited
    `nchildren` - number of children of the node
    `depth` - depth of tree, root node is depth 1.
  Throws:
    `JepException`

### visit

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

  Visit an operator node

  Parameters:
    `node` - the current node being visited
    `nchildren` - number of children of the node
    `depth` - depth of tree, root node is depth 1.
  Throws:
    `JepException`

### visit

    protected abstract void visit(ASTVarNode node,
                                  int nchildren,
                                  int depth)
                           throws JepException

  Visit a variable node

  Parameters:
    `node` - the current node being visited
    `nchildren` - number of children of the node
    `depth` - depth of tree, root node is depth 1.
  Throws:
    `JepException`

### visit

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

  Visit a constant node

  Parameters:
    `node` - the current node being visited
    `nchildren` - number of children of the node
    `depth` - depth of tree, root node is depth 1.
  Throws:
    `JepException`

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Copyright © 2008 Singular Systems http://www.singularsys.com/jep