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.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
   */
  public abstract class Pattern extends Expression {
      /**
       * Returns the type of a pattern, which is always a <code>NodeType</code>.
       * A <code>NodeType</code> has a number of subtypes defined by 
       * <code>NodeType._type</code> corresponding to each type of node.
       */
      public abstract Type typeCheck(SymbolTable stable) throws TypeCheckError;
  
      /**
       * Translate this node into JVM bytecodes. Patterns are translated as
       * boolean expressions with true/false lists. Before calling 
       * <code>translate</code> on a pattern, make sure that the node being 
       * matched is on top of the stack. After calling <code>translate</code>, 
       * make sure to backpatch both true and false lists. True lists are the 
       * default, in the sense that they always <em>"fall through"</em>. If this
       * is not the intended semantics (e.g., see 
       * {@link org.apache.xalan.xsltc.compiler.AlternativePattern#translate})
       * then a GOTO must be appended to the instruction list after calling
       * <code>translate</code>. 
       */
      public abstract void translate(ClassGenerator classGen,
  				   MethodGenerator methodGen);
  
      /**
       * Returns the priority of this pattern (section 5.5 in the XSLT spec).
       */
      public abstract double getPriority();
  }
  