NegativeValueExpression.java

/*
 * Copyright 1999-2012 Alibaba Group.
 * 
 * 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 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.
 */
/**
 * (created at 2011-1-20)
 */
package fm.liu.timo.parser.ast.expression.logical;

import java.util.Map;
import fm.liu.timo.parser.ast.expression.Expression;
import fm.liu.timo.parser.ast.expression.UnaryOperatorExpression;
import fm.liu.timo.parser.ast.expression.primary.literal.LiteralBoolean;
import fm.liu.timo.parser.util.ExprEvalUtils;

/**
 * <code>'!' higherExpr</code>
 * 
 * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
 */
public class NegativeValueExpression extends UnaryOperatorExpression {
    public NegativeValueExpression(Expression operand) {
        super(operand, PRECEDENCE_UNARY_OP);
    }

    @Override
    public String getOperator() {
        return "!";
    }

    @Override
    public Object evaluationInternal(Map<? extends Object, ? extends Object> parameters) {
        Object operand = getOperand().evaluation(parameters);
        if (operand == null)
            return null;
        if (operand == UNEVALUATABLE)
            return UNEVALUATABLE;
        boolean bool = ExprEvalUtils.obj2bool(operand);
        return bool ? LiteralBoolean.FALSE : LiteralBoolean.TRUE;
    }

}