90 lines
4.2 KiB
XML
90 lines
4.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "../dtd/document-v11.dtd">
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<document>
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<header>
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<title>Formula Support</title>
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<authors>
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<person email="avik@apache.org" name="Avik Sengupta" id="AS"/>
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</authors>
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</header>
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<body>
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<section><title>Introduction</title>
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<p>
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This document describes the current state of formula support in POI.
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The information in this document applies to the 2.0-dev version of POI (i.e. CVS HEAD).
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Since this area is a work in progress, this document will be updated with new features as and
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when they are added.
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</p>
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</section>
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<section><title>The basics</title>
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<p>
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In org.apache.poi.hssf.usermodel.HSSFCell
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<strong> setCellFormula("formulaString") </strong> is used to add a formula to sheet and
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<strong> getCellFormula() </strong> is used to retrieve the string representation of a formula.
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</p>
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<p>
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We aim to support the complete excel grammer for formulas. Thus, the string that you pass in
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to the <em> setCellFormula </em> call should be what you expect to type into excel. Also, note
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that you should NOT add a "=" to the front of the string.
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</p>
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</section>
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<section><title>Supported Features</title>
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<ul>
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<li>Cell References</li>
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<li>String, integer and floating point literals</li>
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<li>Area references</li>
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<li>Relative or absolute references</li>
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<li>Arithmetic Operators</li>
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<li>Sheet Functions</li>
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</ul>
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</section>
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<section><title>Partially supported</title>
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<ul>
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<li>
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The formula parser now has the ability to parse formulas containing strings. However
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formulas that return a string value are not yet supported.
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</li>
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<li>Formula tokens in Excel are stored in one of three possible <em> classes </em>:
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Reference, Value and Array. Based on the location of a token, its class can change
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in complicated and undocumented ways. While we have support for most cases, we
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are not sure if we have covered all bases (since there is no documentation for this area.)
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We would therefore like you to report any
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occurence of #VALUE! in a cell upon opening a POI generated workbook in excel. (Check that
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typing the formula into Excel directly gives a valid result.)
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</li>
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</ul>
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</section>
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<section><title>Not yet supported</title>
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<ul>
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<li>Array formulas</li>
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<li>Formulas with logical operations (IF) </li>
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<li>Sheet References in formulas</li>
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<li>Everything else :) </li>
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</ul>
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</section>
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<section><title>Internals</title>
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<p>
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Formulas in Excel are stored as sequences of tokens in Reverse Polish Notation order. The
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<link href="http://sc.openoffice.org/excelfileformat.pdf">open office XLS spec</link> is the best
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documentation you will find for the format.
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</p>
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<p>
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The tokens used by excel are modelled as individual *Ptg classes in the <strong>
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org.apache.poi.hssf.record.formula</strong> package.
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</p>
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<p>
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The task of parsing a formula string into an array of RPN ordered tokens is done by the <strong>
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org.apache.poi.hssf.record.formula.FormulaParser</strong> class. This class implements a hand
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written recursive descent parser.
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</p>
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<p>Check out the <link href="http://jakarta.apache.org/poi/javadocs/">javadocs </link> for details.
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</p>
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</section>
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</body>
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</document> |