001/*
002 * Copyright (C) 2009-2011 Mathias Doenitz
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.parboiled.matchers;
018
019import org.parboiled.MatcherContext;
020import org.parboiled.matchervisitors.MatcherVisitor;
021
022import static org.parboiled.common.Preconditions.checkArgNotNull;
023
024/**
025 * A {@link Matcher} that always successfully matches nothing.
026 */
027public class EmptyMatcher extends AbstractMatcher {
028
029    public EmptyMatcher() {
030        super("EMPTY");
031    }
032
033    public boolean match(MatcherContext context) {
034        context.createNode();
035        return true;
036    }
037
038    public <R> R accept(MatcherVisitor<R> visitor) {
039        checkArgNotNull(visitor, "visitor");
040        return visitor.visit(this);
041    }
042}