code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the  "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.compiler;
  
  import org.apache.bcel.generic.GOTO;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.Type;
  import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
  
  /**
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   */
  final class AlternativePattern extends Pattern {
      private final Pattern _left;
      private final Pattern _right;
  		
      /**
       * Construct an alternative pattern. The method <code>setParent</code>
       * should not be called in this case.
       */
      public AlternativePattern(Pattern left, Pattern right) {
  	_left = left;
  	_right = right;
      }
  		
      public void setParser(Parser parser) {
  	super.setParser(parser);
  	_left.setParser(parser);
  	_right.setParser(parser);
      }
      
      public Pattern getLeft() {
  	return _left;
      }
  
      public Pattern getRight() {
  	return _right;
      }
  
      /**
       * The type of an '|' is not really defined, hence null is returned.
       */
      public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  	_left.typeCheck(stable);
  	_right.typeCheck(stable);
  	return null;
      }
  
      public double getPriority() {
  	double left = _left.getPriority();
  	double right = _right.getPriority();
  	
  	if (left < right)
  	    return(left);
  	else
  	    return(right);
      }
  
      public String toString() {
  	return "alternative(" + _left + ", " + _right + ')';
      }
  
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	final InstructionList il = methodGen.getInstructionList();
  
  	_left.translate(classGen, methodGen);
  	final InstructionHandle gotot = il.append(new GOTO(null));
  	il.append(methodGen.loadContextNode());
  	_right.translate(classGen, methodGen);
  
  	_left._trueList.backPatch(gotot);
  	_left._falseList.backPatch(gotot.getNext());
  
  	_trueList.append(_right._trueList.add(gotot));
  	_falseList.append(_right._falseList);
      }
  }
  