source: trunk/yao/share/antlr-2.7.7/antlr/ParseTree.java @ 1

package antlr;

/* ANTLR Translator Generator
 * Project led by Terence Parr at http://www.cs.usfca.edu
 * Software rights: http://www.antlr.org/license.html
 */

import antlr.*;
import antlr.collections.AST;

public abstract class ParseTree extends BaseAST {

        /** Walk parse tree and return requested number of derivation steps.
         *  If steps <= 0, return node text.  If steps == 1, return derivation
         *  string at step.
         */
        public String getLeftmostDerivationStep(int step) {
        if ( step<=0 ) {
                        return toString();
                }
                StringBuffer buf = new StringBuffer(2000);
        getLeftmostDerivation(buf, step);
                return buf.toString();
        }

        public String getLeftmostDerivation(int maxSteps) {
                StringBuffer buf = new StringBuffer(2000);
                buf.append("    "+this.toString());
                buf.append("\n");
                for (int d=1; d<maxSteps; d++) {
                        buf.append(" =>");
                        buf.append(getLeftmostDerivationStep(d));
                        buf.append("\n");
                }
                return buf.toString();
        }

        /** Get derivation and return how many you did (less than requested for
         *  subtree roots.
         */
        protected abstract int getLeftmostDerivation(StringBuffer buf, int step);

        // just satisfy BaseAST interface; unused as we manually create nodes

        public void initialize(int i, String s) {
        }
        public void initialize(AST ast) {
        }
        public void initialize(Token token) {
        }
}