production.java

Grammatica是一个C#和Java的语法分析程序生成器(编译器的编译器)。它可以用LL(k)语法创建可读的和带有注释的源代码。它也支持创建一个运行时语法分析器

/*
 * Production.java
 *
 * This work is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License,
 * or (at your option) any later version.
 *
 * This work is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software 
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 *
 * As a special exception, the copyright holders of this library give
 * you permission to link this library with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also meet,
 * for each linked independent module, the terms and conditions of the
 * license of that module. An independent module is a module which is
 * not derived from or based on this library. If you modify this
 * library, you may extend this exception to your version of the
 * library, but you are not obligated to do so. If you do not wish to
 * do so, delete this exception statement from your version.
 *
 * Copyright (c) 2003 Per Cederberg. All rights reserved.
 */

package net.percederberg.grammatica.parser;

import java.util.ArrayList;

/**
 * A production node. This class represents a grammar production (i.e.
 * a list of child nodes) in a parse tree. The productions are created 
 * by a parser, that adds children a according to a set of production
 * patterns (i.e. grammar rules).
 *
 * @author   Per Cederberg, <per at percederberg dot net>
 * @version  1.1
 */
public class Production extends Node {

    /**
     * The production pattern used for this production.
     */
    private ProductionPattern pattern;

    /**
     * The child nodes.
     */
    private ArrayList children;

    /**
     * Creates a new production node.
     * 
     * @param pattern        the production pattern
     */
    public Production(ProductionPattern pattern) {
        this.pattern = pattern;
        this.children = new ArrayList();
    }

    /**
     * Checks if this node is hidden, i.e. if it should not be visible
     * outside the parser.
     * 
     * @return true if the node should be hidden, or
     *         false otherwise
     */
    boolean isHidden() {
        return pattern.isSyntetic();
    }

    /**
     * Returns the production pattern for this production.
     * 
     * @return the production pattern
     */
    public ProductionPattern getPattern() {
        return pattern;
    }

    /**
     * Returns the production (pattern) id. This value is set as a 
     * unique identifier when creating the production pattern to 
     * simplify later identification.
     * 
     * @return the production id
     */
    public int getId() {
        return pattern.getId();    
    }
    
    /**
     * Returns the production node name.
     * 
     * @return the production node name
     */
    public String getName() {
        return pattern.getName();
    }

    /**
     * Returns the number of child nodes.
     * 
     * @return the number of child nodes
     */
    public int getChildCount() {
        return children.size();
    }

    /**
     * Returns the child node with the specified index.
     * 
     * @param index          the child index, 0 <= index < count
     * 
     * @return the child node found, or 
     *         null if index out of bounds
     */
    public Node getChildAt(int index) {
        if (index < 0 || index >= children.size()) {
            return null; 
        } else {
            return (Node) children.get(index);
        }
    }
    
    /**
     * Adds a child node. The node will be added last in the list of
     * children.
     * 
     * @param child          the child node to add
     */
    public void addChild(Node child) {
        if (child != null) {
            child.setParent(this);
            children.add(child);
        }
    }

    /**
     * Returns a string representation of this production.
     * 
     * @return a string representation of this production
     */
    public String toString() {
        StringBuffer  buffer = new StringBuffer();

        buffer.append(pattern.getName());
        buffer.append('(');
        buffer.append(pattern.getId());
        buffer.append(')');
        
        return buffer.toString();        
    }
}