operationeval.java

java 读写word excel ppt

/*
* 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.
*/
/*
 * Created on May 8, 2005
 *
 */
package org.apache.poi.hssf.record.formula.eval;

/**
 * @author Amol S. Deshmukh < amolweb at ya hoo dot com >
 *  
 */
public interface OperationEval extends Eval {

    /*
     * Read this, this will make your work easier when coding 
     * an "evaluate()"
     * 
     * Things to note when implementing evaluate():
     * 1. Check the length of operands
     *    (use "switch(operands[x])" if possible)
     * 
     * 2. The possible Evals that you can get as args to evaluate are one of:
     * NumericValueEval, StringValueEval, RefEval, AreaEval
     * 3. If it is RefEval, the innerValueEval could be one of:
     * NumericValueEval, StringValueEval, BlankEval
     * 4. If it is AreaEval, each of the values could be one of:
     * NumericValueEval, StringValueEval, BlankEval, RefEval
     * 
     * 5. For numeric functions/operations, keep the result in double
     * till the end and before returning a new NumberEval, check to see
     * if the double is a NaN - if NaN, return ErrorEval.ERROR_503 
     */
    public abstract Eval evaluate(Eval[] evals, int srcCellRow, short srcCellCol);

    public abstract int getNumberOfOperands();

    public abstract int getType();
}