asterix-om/src/main/java/edu/uci/ics/asterix/om/typecomputer/impl/TripleStringStringOrNullTypeComputer.java

/*
 * Copyright 2009-2013 by The Regents of the University of California
 * Licensed 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 from
 * 
 *     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.
 */
package edu.uci.ics.asterix.om.typecomputer.impl;

import edu.uci.ics.asterix.om.types.AUnionType;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.om.types.IAType;
import edu.uci.ics.asterix.om.types.TypeHelper;

/**
 * @author Xiaoyu Ma
 */
public class TripleStringStringOrNullTypeComputer extends AbstractTripleStringTypeComputer {
    public static final TripleStringStringOrNullTypeComputer INSTANCE = new TripleStringStringOrNullTypeComputer();

    private TripleStringStringOrNullTypeComputer() {
    }

    @Override
    public IAType getResultType(IAType t0, IAType t1, IAType t2) {
        if (TypeHelper.canBeNull(t0) || TypeHelper.canBeNull(t1) || TypeHelper.canBeNull(t2)) {
            return AUnionType.createNullableType(BuiltinType.ASTRING);
        }
        return BuiltinType.ASTRING;
    }
}