javacc-7.0.1.examples.JJTreeExamples.java.Eg4DumpVisitor Maven / Gradle / Ivy

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JavaCC is a parser/scanner generator for Java.
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/* Copyright (c) 2006, Sun Microsystems, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Sun Microsystems, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 *  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.
 *  
 *   the visitor can maintain state between the nodes that it visits
 *  (for example the current indentation level).
 *  
 *
 *  if you don't implement a jjtAccept() method for a subclass of
 *  SimpleNode, then SimpleNode's acceptor will get called.
 *  
 *   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*/