poi/src/java/org/apache/poi/ss/formula/functions/Vlookup.java

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   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
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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.BoolEval;
import org.apache.poi.ss.formula.eval.EvaluationException;
import org.apache.poi.ss.formula.eval.OperandResolver;
import org.apache.poi.ss.formula.eval.ValueEval;
import org.apache.poi.ss.formula.functions.LookupUtils.ValueVector;
import org.apache.poi.ss.formula.TwoDEval;
/**
 * Implementation of the VLOOKUP() function.<p/>
 *
 * VLOOKUP finds a row in a lookup table by the first column value and returns the value from another column.<br/>
 *
 * <b>Syntax</b>:<br/>
 * <b>VLOOKUP</b>(<b>lookup_value</b>, <b>table_array</b>, <b>col_index_num</b>, range_lookup)<p/>
 *
 * <b>lookup_value</b>  The value to be found in the first column of the table array.<br/>
 * <b>table_array</b> An area reference for the lookup data. <br/>
 * <b>col_index_num</b> a 1 based index specifying which column value of the lookup data will be returned.<br/>
 * <b>range_lookup</b> If TRUE (default), VLOOKUP finds the largest value less than or equal to
 * the lookup_value.  If FALSE, only exact matches will be considered<br/>
 *
 * @author Josh Micich
 * @author Cedric Walter at innoveo.com
 */
public final class Vlookup extends Var3or4ArgFunction {
	private static final ValueEval DEFAULT_ARG3 = BoolEval.TRUE;

	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
			ValueEval arg2) {
		return evaluate(srcRowIndex, srcColumnIndex, arg0, arg1, arg2, DEFAULT_ARG3);
	}

	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval lookup_value, ValueEval table_array,
			ValueEval col_index, ValueEval range_lookup) {
		try {
			// Evaluation order:
			// lookup_value , table_array, range_lookup, find lookup value, col_index, fetch result
			ValueEval lookupValue = OperandResolver.getSingleValue(lookup_value, srcRowIndex, srcColumnIndex);
			TwoDEval tableArray = LookupUtils.resolveTableArrayArg(table_array);
			boolean isRangeLookup = LookupUtils.resolveRangeLookupArg(range_lookup, srcRowIndex, srcColumnIndex);
			int rowIndex = LookupUtils.lookupIndexOfValue(lookupValue, LookupUtils.createColumnVector(tableArray, 0), isRangeLookup);
			int colIndex = LookupUtils.resolveRowOrColIndexArg(col_index, srcRowIndex, srcColumnIndex);
			ValueVector resultCol = createResultColumnVector(tableArray, colIndex);
			return resultCol.getItem(rowIndex);
		} catch (EvaluationException e) {
			return e.getErrorEval();
		}
	}


	/**
	 * Returns one column from an <tt>AreaEval</tt>
	 *
	 * @param colIndex assumed to be non-negative
	 *
	 * @throws EvaluationException (#REF!) if colIndex is too high
	 */
	private ValueVector createResultColumnVector(TwoDEval tableArray, int colIndex) throws EvaluationException {
		if(colIndex >= tableArray.getWidth()) {
			throw EvaluationException.invalidRef();
		}
		return LookupUtils.createColumnVector(tableArray, colIndex);
	}
}