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   this work for additional information regarding copyright ownership.
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   (the "License"); you may not use this file except in compliance with
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   distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.poi.ss.formula.functions;

import org.apache.poi.ss.formula.eval.AreaEval;
import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.RefEval;
import org.apache.poi.ss.formula.eval.StringEval;
import org.apache.poi.ss.formula.eval.ValueEval;

Implementation of Excel T() function

If the argument is a text or error value it is returned unmodified.  All other argument types
cause an empty string result.  If the argument is an area, the first (top-left) cell is used
(regardless of the coordinates of the evaluating formula cell).
/**
 * Implementation of Excel T() function
 * <p>
 * If the argument is a text or error value it is returned unmodified.  All other argument types
 * cause an empty string result.  If the argument is an area, the first (top-left) cell is used
 * (regardless of the coordinates of the evaluating formula cell).
 */
public final class T extends Fixed1ArgFunction {

    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
        ValueEval arg = arg0;
        if (arg instanceof RefEval) {
            // always use the first sheet
            RefEval re = (RefEval)arg;
            arg = re.getInnerValueEval(re.getFirstSheetIndex());
        } else if (arg instanceof AreaEval) {
            // when the arg is an area, choose the top left cell
            arg = ((AreaEval) arg).getRelativeValue(0, 0);
        }

        if (arg instanceof StringEval) {
            // Text values are returned unmodified
            return arg;
        }

        if (arg instanceof ErrorEval) {
            // Error values also returned unmodified
            return arg;
        }
        // for all other argument types the result is empty string
        return StringEval.EMPTY_INSTANCE;
    }
}