| /* ==================================================================== |
| 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. |
| ==================================================================== */ |
| |
| package org.apache.poi.ss.formula.functions; |
| |
| import org.apache.poi.ss.formula.eval.ValueEval; |
| import org.apache.poi.ss.formula.OperationEvaluationContext; |
| |
| |
| /** |
| * For most Excel functions, involving references ((cell, area), (2d, 3d)), the references are |
| * passed in as arguments, and the exact location remains fixed. However, a select few Excel |
| * functions have the ability to access cells that were not part of any reference passed as an |
| * argument.<br> |
| * Two important functions with this feature are <b>INDIRECT</b> and <b>OFFSET</b><p> |
| * |
| * When POI evaluates formulas, each reference argument is capable of evaluating any cell inside |
| * its range. Actually, even cells outside the reference range but on the same sheet can be |
| * evaluated. This allows <b>OFFSET</b> to be implemented like most other functions - taking only |
| * the arguments, and source cell coordinates. |
| * |
| * For the moment this interface only exists to serve the <b>INDIRECT</b> which can decode |
| * arbitrary text into cell references, and evaluate them.. |
| * |
| * @author Josh Micich |
| */ |
| public interface FreeRefFunction { |
| /** |
| * @param args the pre-evaluated arguments for this function. args is never <code>null</code>, |
| * nor are any of its elements. |
| * @param ec primarily used to identify the source cell containing the formula being evaluated. |
| * may also be used to dynamically create reference evals. |
| * @return never <code>null</code>. Possibly an instance of <tt>ErrorEval</tt> in the case of |
| * a specified Excel error (Exceptions are never thrown to represent Excel errors). |
| */ |
| ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec); |
| } |