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eg4DumpVisitor.java

/*
 * Copyright © 2002 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * California 95054, U.S.A. All rights reserved.  Sun Microsystems, Inc. has
 * intellectual property rights relating to technology embodied in the product
 * that is described in this document. In particular, and without limitation,
 * these intellectual property rights may include one or more of the U.S.
 * patents listed at http://www.sun.com/patents and one or more additional
 * patents or pending patent applications in the U.S. and in other countries.
 * U.S. Government Rights - Commercial software. Government users are subject
 * to the Sun Microsystems, Inc. standard license agreement and applicable
 * provisions of the FAR and its supplements.  Use is subject to license terms.
 * Sun,  Sun Microsystems,  the Sun logo and  Java are trademarks or registered
 * trademarks of Sun Microsystems, Inc. in the U.S. and other countries.  This
 * product is covered and controlled by U.S. Export Control laws and may be
 * subject to the export or import laws in other countries.  Nuclear, missile,
 * chemical biological weapons or nuclear maritime end uses or end users,
 * whether direct or indirect, are strictly prohibited.  Export or reexport
 * to countries subject to U.S. embargo or to entities identified on U.S.
 * export exclusion lists, including, but not limited to, the denied persons
 * and specially designated nationals lists is strictly prohibited.
 */


/* This is an example of how the Visitor pattern might be used to
   implement the dumping code that comes with SimpleNode.  It's a bit
   long-winded, but it does illustrate a couple of the main points.

   1) the visitor can maintain state between the nodes that it visits
   (for example the current indentation level).

   2) if you don't implement a jjtAccept() method for a subclass of
   SimpleNode, then SimpleNode's acceptor will get called.

   3) the utility method childrenAccept() can be useful when
   implementing preorder or postorder tree walks.

*/

public class eg4DumpVisitor implements eg4Visitor
{
  private int indent = 0;

  private String indentString() {
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < indent; ++i) {
      sb.append(" ");
    }
    return sb.toString();
  }

  public Object visit(SimpleNode node, Object data) {
    System.out.println(indentString() + node +
                   ": acceptor not unimplemented in subclass?");
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }

  public Object visit(ASTStart node, Object data) {
    System.out.println(indentString() + node);
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }

  public Object visit(ASTAdd node, Object data) {
    System.out.println(indentString() + node);
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }

  public Object visit(ASTMult node, Object data) {
    System.out.println(indentString() + node);
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }

  public Object visit(ASTMyOtherID node, Object data) {
    System.out.println(indentString() + node);
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }

  public Object visit(ASTInteger node, Object data) {
    System.out.println(indentString() + node);
    ++indent;
    data = node.childrenAccept(this, data);
    --indent;
    return data;
  }
}

/*end*/

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