package rebelsky.compiler.parser;

import java.io.PrintWriter;

/**
 * A simple mechanism for printing parse trees.  Intended mostly
 * as a debugging aid.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of October 2002
 */
public class TreePrinter
{
  private static final String indent = "  ";

  /**
   * Dump a tree to the given output object.
   *
   * Pre: obj is either a Node or a Token.
   */
  public static void print(Node root, PrintWriter out)
  {
    print(root, out, "");
  } // print(Object,PrintWriter)

  private static void print(Node root, PrintWriter out, String offset) 
  {
    // Special case: The thing to be printed is null.  I don't think
    //  this should happen, but it's good to be careful.  In this
    //  case, print nothing.
    if (root == null) {
    }
    // Standard case: A Node
    //   Print the symbol
    //   Print the children
    else {
      out.println(offset + root.getSymbol().toString());
      int numChildren = root.numChildren();
      for (int childNum = 0; childNum < numChildren; ++childNum) {
        print(root.getChild(childNum), out, offset+indent);
      } // for each child
    } // if the object is a node.
  } // print(Object, PrintWriter, String)
} // class TreePrinter