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polished code to register new function impls in runtime

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git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1293851 13f79535-47bb-0310-9956-ffa450edef68
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Yegor Kozlov 2012-02-26 15:22:43 +00:00
parent 582ea1c54c
commit d1d0ea3692
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395
src/documentation/content/xdocs/spreadsheet/eval-devguide.xml
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@ -24,21 +24,29 @@
<title>Developing Formula Evaluation</title>
<authors>
<person email="amoweb@yahoo.com" name="Amol Deshmukh" id="AD"/>
<person email="yegor@apache.org" name="Yegor Kozlov" id="YK"/>
</authors>
</header>
<body>
<section><title>Introduction</title>
<p>This document is for developers wishing to contribute to the
FormulaEvaluator API functionality.</p>
<p>Currently, contribution is desired for implementing the standard MS
<p>When evaluating workbooks you may encounter a org.apache.poi.ss.formula.eval.NotImplementedException
which indicates that a function is not (yet) supported by POI. Is there a workaround?
Yes, the POI framework makes it easy to add implementation of new functions. Prior to POI-3.8
you had to checkout the source code from svn and make a custom build with your function implementation.
Since POI-3.8 you can register new functions in run-time.
</p>
<p>Currently, contribution is desired for implementing the standard MS
excel functions. Place holder classes for these have been created,
contributors only need to insert implementation for the
individual "evaluate()" methods that do the actual evaluation.</p>
</section>
<section><title>Overview of FormulaEvaluator </title>
<p>Briefly, a formula string (along with the sheet and workbook that
form the context in which the formula is evaluated) is first parsed
into RPN tokens using the FormulaParser class in POI-HSSF main.
into RPN tokens using the FormulaParser class .
(If you dont know what RPN tokens are, now is a good time to
read <link href="http://www-stone.ch.cam.ac.uk/documentation/rrf/rpn.html">
this</link>.)
@ -65,7 +73,7 @@
eventually there are no more RPN tokens at which point, if the formula
string was correctly parsed, there should be just one Eval on the
stack - which contains the result of evaluating the formula.</p>
<p>Ofcourse I glossed over the details of how AreaPtg and ReferencePtg
<p>Of course I glossed over the details of how AreaPtg and ReferencePtg
are handled a little differently, but the code should be self
explanatory for that. Very briefly, the cells included in AreaPtg and
RefPtg are examined and their values are populated in individual
@ -74,131 +82,276 @@
AreaEval and RefEval - but you'll figure all that out from the code)</p>
<p>OperationEvals for the standard operators have been implemented and tested.</p>
</section>
<section><title> FunctionEval and FuncVarEval</title>
<p>FunctionEval is an abstract super class of FuncVarEval. The reason for this is that in the FormulaParser Ptg classes, there are two Ptgs, FuncPtg and FuncVarPtg. In my tests, I did not see FuncPtg being used so there is no corresponding FuncEval right now. But in case the need arises for a FuncVal class, FuncEval and FuncVarEval need to be isolated with a common interface/abstract class, hence FunctionEval.</p>
<p>FunctionEval also contains the mapping of which function class maps to which function index. This mapping has been done for all the functions, so all you really have to do is implement the evaluate method in the function class that has not already been implemented. The Function indexes are defined in AbstractFunctionPtg class in POI main.</p>
</section>
</section>
<section><title>Walkthrough of an "evaluate()" implementation.</title>
<p>So here is the fun part - lets walk through the implementation of the excel
function... <strong>SQRT()</strong> </p>
<section><title>The Code</title>
<source>
public class Sqrt extends NumericFunction {
private static final ValueEvalToNumericXlator NUM_XLATOR =
new ValueEvalToNumericXlator((short)
( ValueEvalToNumericXlator.BOOL_IS_PARSED
| ValueEvalToNumericXlator.EVALUATED_REF_BOOL_IS_PARSED
| ValueEvalToNumericXlator.EVALUATED_REF_STRING_IS_PARSED
| ValueEvalToNumericXlator.REF_BOOL_IS_PARSED
| ValueEvalToNumericXlator.STRING_IS_PARSED
));
protected ValueEvalToNumericXlator getXlator() {
return NUM_XLATOR;
<section><title>What functions are supported?</title>
<p>
As of Feb 2012, POI supports about 140 built-in functions,
see <link href="#appendixA">Appendix A</link> for the full list.
You can programmatically list supported / unsuported functions using trhe following helper methods:
</p>
<source>
// list of functions that POI can evaluate
Collection&lt;String&gt; suportedFuncs = WorkbookEvaluator.getSupportedFunctionNames();
// list of functions that are not supported by POI
Collection&lt;String&gt; unsupportedFuncs = WorkbookEvaluator.getNotSupportedFunctionNames();
</source>
</section>
<section><title>Two base interfaces to start your implementation</title>
<p>
All Excel formula function classes implement either
org.apache.poi.hssf.record.formula.functions.Function or
org.apache.poi.hssf.record.formula.functions.FreeRefFunction interface.
Function is a commonn interface for the functions defined in the binary Excel format (BIFF8): these are "classic" Excel functions like SUM, COUNT, LOOKUP, etc.
FreeRefFunction is a common interface for the functions from the Excel Analysis Toolpack and for User-Defined Functions.
In the future these two interfaces are expected be unified into one, but for now you have to start your implementation from two slightly different roots.
</p>
</section>
<section><title>Which interface to start from?</title>
<p>
You are about to implement a function XXX and don't know which interface to start from: Function or FreeRefFunction.
Use the following code to check whether your function is from the excel Analysis Toolpack:
</p>
<source>
if(AnalysisToolPack.isATPFunction(functionName)){
// the function implements org.apache.poi.hssf.record.formula.functions.Function
} else {
// the function implements org.apache.poi.hssf.record.formula.functions.FreeRefFunction
}
</source>
</section>
public Eval evaluate(Eval[] operands, int srcRow, short srcCol) {
double d = 0;
ValueEval retval = null;
switch (operands.length) {
default:
retval = ErrorEval.VALUE_INVALID;
break;
case 1:
ValueEval ve = singleOperandEvaluate(operands[0], srcRow, srcCol);
if (ve instanceof NumericValueEval) {
NumericValueEval ne = (NumericValueEval) ve;
d = ne.getNumberValue();
}
else if (ve instanceof BlankEval) {
// do nothing
}
else {
retval = ErrorEval.NUM_ERROR;
<section><title>Walkthrough of an "evaluate()" implementation.</title>
<p>Here is the fun part: lets walk through the implementation of the excel function <strong>SQRT()</strong>
</p>
<p>
AnalysisToolPack.isATPFunction("SQRTPI") returns false so the base interface is Function.
There are sub-interfaces that make life easier when implementing numeric functions or functions
with fixed number of arguments, 1-arg, 2-arg and 3-arg function:
</p>
<ul>
<li>org.apache.poi.hssf.record.formula.functions.NumericFunction</li>
<li>org.apache.poi.hssf.record.formula.functions.Fixed1ArgFunction</li>
<li>org.apache.poi.hssf.record.formula.functions.Fixed2ArgFunction</li>
<li>org.apache.poi.hssf.record.formula.functions.Fixed3ArgFunction</li>
<li>org.apache.poi.hssf.record.formula.functions.Fixed4ArgFunction</li>
</ul>
<p>
Since SQRTPI takes exactly one argument we start our implementation from org.apache.poi.hssf.record.formula.functions.Fixed1ArgFunction:
</p>
<source>
Function SQRTPI = new Fixed1ArgFunction() {
public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0) {
try {
// Retrieves a single value from a variety of different argument types according to standard
// Excel rules. Does not perform any type conversion.
ValueEval ve = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
// Applies some conversion rules if the supplied value is not already a number.
// Throws EvaluationException(#VALUE!) if the supplied parameter is not a number
double arg = OperandResolver.coerceValueToDouble(ve);
// this where all the heavy-lifting happens
double result = Math.sqrt(arg*Math.PI);
// Excel uses the error code #NUM! instead of IEEE <em>NaN</em> and <em>Infinity</em>,
// so when a numeric function evaluates to Double.NaN or Double.Infinity,
// be sure to translate the result to the appropriate error code
if (Double.isNaN(result) || Double.isInfinite(result)) {
throw new EvaluationException(ErrorEval.NUM_ERROR);
}
return new NumberEval(result);
} catch (EvaluationException e){
return e.getErrorEval();
}
}
if (retval == null) {
d = Math.sqrt(d);
retval = (Double.isNaN(d)) ? (ValueEval) ErrorEval.VALUE_INVALID : new NumberEval(d);
}
return retval;
}
</source>
}
</source>
</section>
<section><title>Implementation Details</title>
<ul>
<li>The first thing to realise is that classes already exist, even for functions that are not yet implemented.
Just that they extend from DefaultFunctionImpl whose behaviour is to return an ErrorEval.FUNCTION_NOT_IMPLEMENTED value.</li>
<li>In order to implement SQRT(..), we need to: a. Extend from the correct Abstract super class; b. implement the evaluate(..) method</li>
<li>Hence we extend SQRT(..) from the predefined class NumericFunction</li>
<li>Since SQRT(..) takes a single argument, we verify the length of the operands array else set the return value to ErrorEval.VALUE_INVALID</li>
<li>Next we normalize each operand to a limited set of ValueEval subtypes, specifically, we call the function
<code>singleOperandEvaluate(..)</code> to do conversions of different value eval types to one of: NumericValueEval,
BlankEval and ErrorEval. The conversion logic is configured by a ValueEvalToNumericXlator instance which
is returned by the Factory method: <code>getXlator(..)</code> The flags used to create the ValueEvalToNumericXlator
instance are briefly explained as follows:
BOOL_IS_PARSED means whether this function treats Boolean values as 1,
REF_BOOL_IS_PARSED means whether Boolean values in cell references are parsed or not.
So also, EVALUATED_REF_BOOL_IS_PARSED means if the operand was a RefEval that was assigned a
Boolean value as a result of evaluation of the formula that it contained.
eg. SQRT(TRUE) returns 1: This means BOOL_IS_PARSED should be set.
SQRT(A1) returns 1 when A1 has TRUE: This means REF_BOOL_IS_PARSED should be set.
SQRT(A1) returns 1 when A1 has a formula that evaluates to TRUE: This means EVALUATED_REF_BOOL_IS_PARSED should be set.
If the flag is not set for a particular case, that case is ignored (treated as if the cell is blank) _unless_
there is a flag like: STRING_IS_INVALID_VALUE (which means that Strings should be treated as resulting in VALUE_INVALID ErrorEval)
</li>
<li>Next perform the appropriate Math function on the double value (if an error didnt occur already).</li>
<li>Finally before returning the NumberEval wrapping the double value that
you computed, do one final check to see if the double is a NaN, (or if it is "Infinite")
If it is return the appropriate ErrorEval instance. Note: The OpenOffice.org error codes
should NOT be preferred. Instead use the excel specific error codes like VALUE_INVALID, NUM_ERROR, DIV_ZERO etc.
(Thanks to Avik for bringing this issue up early!) The Oo.o ErrorCodes will be removed (if they havent already been :)</li>
</ul>
</section>
<section><title>Modelling Excel Semantics</title>
<p>Strings are ignored. Booleans are ignored!!!. Actually here's the info on Bools:
if you have formula: "=TRUE+1", it evaluates to 2.
So also, when you use TRUE like this: "=SUM(1,TRUE)", you see the result is: 2.
So TRUE means 1 when doing numeric calculations, right?
Wrong!
Because when you use TRUE in referenced cells with arithmetic functions, it evaluates to blank - meaning it is not evaluated - as if it was string or a blank cell.
eg. "=SUM(1,A1)" when A1 is TRUE evaluates to 1.
This behaviour changes depending on which function you are using. eg. SQRT(..) that was
described earlier treats a TRUE as 1 in all cases. This is why the configurable ValueEvalToNumericXlator
class had to be written.
</p>
<p>Note that when you are extending from an abstract function class like
NumericFunction (rather than implementing the interface o.a.p.hssf.record.formula.eval.Function directly)
you can use the utility methods in the super class - singleOperandEvaluate(..) - to quickly
reduce the different ValueEval subtypes to a small set of possible types. However when
implemenitng the Function interface directly, you will have to handle the possiblity
of all different ValueEval subtypes being sent in as 'operands'. (Hard to put this in
word, please have a look at the code for NumericFunction for an example of
how/why different ValueEvals need to be handled)
</p>
</section>
</section>
<section><title>Testing Framework</title>
<p>Automated testing of the implemented Function is easy.
The source code for this is in the file: o.a.p.h.record.formula.GenericFormulaTestCase.java
This class has a reference to the test xls file (not /a/ test xls, /the/ test xls :)
which may need to be changed for your environment. Once you do that, in the test xls,
locate the entry for the function that you have implemented and enter different tests
in a cell in the FORMULA row. Then copy the "value of" the formula that you entered in the
cell just below it (this is easily done in excel as:
[copy the formula cell] > [go to cell below] > Edit > Paste Special > Values > "ok").
You can enter multiple such formulas and paste their values in the cell below and the
test framework will automatically test if the formula evaluation matches the expected
value (Again, hard to put in words, so if you will, please take time to quickly look
at the code and the currently entered tests in the patch attachment "FormulaEvalTestData.xls"
file).
</p>
</section>
<p>Now when the implementation is ready we need to register it in the formula evaluator:</p>
<source>
WorkbookEvaluator.registerFunction("SQRTPI", SQRTPI);
</source>
<p>Voila! The formula evaluator now recognizes SQRTPI! </p>
</section>
<section><title>Floating-point Arithmetic in Excel</title>
<p>Excel uses the IEEE Standard for Double Precision Floating Point numbers
except two cases where it does not adhere to IEEE 754:
</p>
<ol>
<li>Positive/Negative Infinities: Infinities occur when you divide by 0.
Excel does not support infinities, rather, it gives a #DIV/0! error in these cases.
</li>
<li>Not-a-Number (NaN): NaN is used to represent invalid operations
(such as infinity/infinity, infinity-infinity, or the square root of -1).
NaNs allow a program to continue past an invalid operation.
Excel instead immediately generates an error such as #NUM! or #DIV/0!.
</li>
</ol>
<p>Be aware of these two cases when saving results of your scientific calculations in Excel:
“where are my Infinities and NaNs? They are gone!”
</p>
</section>
<anchor id="appendixA"/>
<section>
<title>Appendix A</title>
<p>Functions supported by POI ( as of Feb 2012)</p>
<source>
ABS
ACOS
ACOSH
ADDRESS
AND
ASIN
ASINH
ATAN
ATAN2
ATANH
AVEDEV
AVERAGE
CEILING
CHAR
CHOOSE
CLEAN
COLUMN
COLUMNS
COMBIN
CONCATENATE
COS
COSH
COUNT
COUNTA
COUNTBLANK
COUNTIF
DATE
DAY
DAYS360
DEGREES
DEVSQ
DOLLAR
ERROR.TYPE
EVEN
EXACT
EXP
FACT
FALSE
FIND
FLOOR
FV
HLOOKUP
HOUR
HYPERLINK
IF
INDEX
INDIRECT
INT
IRR
ISBLANK
ISERROR
ISEVEN
ISLOGICAL
ISNA
ISNONTEXT
ISNUMBER
ISODD
ISREF
ISTEXT
LARGE
LEFT
LEN
LN
LOG
LOG10
LOOKUP
LOWER
MATCH
MAX
MAXA
MEDIAN
MID
MIN
MINA
MINUTE
MOD
MODE
MONTH
MROUND
NA
NETWORKDAYS
NOT
NOW
NPER
NPV
ODD
OFFSET
OR
PI
PMT
POISSON
POWER
PRODUCT
PV
RADIANS
RAND
RANDBETWEEN
RATE
REPLACE
RIGHT
ROUND
ROUNDDOWN
ROUNDUP
ROW
ROWS
SEARCH
SECOND
SIGN
SIN
SINH
SMALL
SQRT
STDEV
SUBSTITUTE
SUBTOTAL
SUM
SUMIF
SUMIFS
SUMPRODUCT
SUMSQ
SUMX2MY2
SUMX2PY2
SUMXMY2
T
TAN
TANH
TEXT
TIME
TODAY
TRIM
TRUE
TRUNC
UPPER
VALUE
VAR
VARP
VLOOKUP
WORKDAY
YEAR
YEARFRAC
</source>
</section>
</body>
</document>

2
src/documentation/content/xdocs/spreadsheet/eval.xml
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@ -41,7 +41,7 @@
<anchor id="Status"/>
<section><title>Status</title>
<p> The code currently provides implementations for all the arithmatic operators.
It also provides implementations for approx. 100 built in
It also provides implementations for approx. 140 built in
functions in Excel. The framework however makes is easy to add
implementation of new functions. See the <link href="eval-devguide.html"> Formula
evaluation development guide</link> and <link href="../apidocs/org/apache/poi/hssf/record/formula/functions/package-summary.html">javadocs</link>

66
src/java/org/apache/poi/ss/formula/WorkbookEvaluator.java
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@ -17,10 +17,11 @@
package org.apache.poi.ss.formula;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.Stack;
import java.util.*;
import org.apache.poi.ss.formula.atp.AnalysisToolPak;
import org.apache.poi.ss.formula.eval.*;
import org.apache.poi.ss.formula.functions.Function;
import org.apache.poi.ss.formula.ptg.Area3DPtg;
import org.apache.poi.ss.formula.ptg.AreaErrPtg;
import org.apache.poi.ss.formula.ptg.AreaPtg;
@ -48,16 +49,6 @@ import org.apache.poi.ss.formula.ptg.RefPtg;
import org.apache.poi.ss.formula.ptg.StringPtg;
import org.apache.poi.ss.formula.ptg.UnionPtg;
import org.apache.poi.ss.formula.ptg.UnknownPtg;
import org.apache.poi.ss.formula.eval.BlankEval;
import org.apache.poi.ss.formula.eval.BoolEval;
import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.EvaluationException;
import org.apache.poi.ss.formula.eval.MissingArgEval;
import org.apache.poi.ss.formula.eval.NameEval;
import org.apache.poi.ss.formula.eval.NumberEval;
import org.apache.poi.ss.formula.eval.OperandResolver;
import org.apache.poi.ss.formula.eval.StringEval;
import org.apache.poi.ss.formula.eval.ValueEval;
import org.apache.poi.ss.formula.functions.Choose;
import org.apache.poi.ss.formula.functions.FreeRefFunction;
import org.apache.poi.ss.formula.functions.IfFunc;
@ -65,7 +56,6 @@ import org.apache.poi.ss.formula.udf.AggregatingUDFFinder;
import org.apache.poi.ss.formula.udf.UDFFinder;
import org.apache.poi.ss.util.CellReference;
import org.apache.poi.ss.formula.CollaboratingWorkbooksEnvironment.WorkbookNotFoundException;
import org.apache.poi.ss.formula.eval.NotImplementedException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.util.POILogFactory;
import org.apache.poi.util.POILogger;
@ -685,4 +675,52 @@ public final class WorkbookEvaluator {
public void setIgnoreMissingWorkbooks(boolean ignore){
_ignoreMissingWorkbooks = ignore;
}
/**
* Return a collection of functions that POI can evaluate
*
* @return names of functions supported by POI
*/
public static Collection<String> getSupportedFunctionNames(){
Collection<String> lst = new TreeSet<String>();
lst.addAll(FunctionEval.getSupportedFunctionNames());
lst.addAll(AnalysisToolPak.getSupportedFunctionNames());
return lst;
}
/**
* Return a collection of functions that POI does not support
*
* @return names of functions NOT supported by POI
*/
public static Collection<String> getNotSupportedFunctionNames(){
Collection<String> lst = new TreeSet<String>();
lst.addAll(FunctionEval.getNotSupportedFunctionNames());
lst.addAll(AnalysisToolPak.getNotSupportedFunctionNames());
return lst;
}
/**
* Register a ATP function in runtime.
*
* @param name the function name
* @param func the functoin to register
* @throws IllegalArgumentException if the function is unknown or already registered.
* @since 3.8 beta6
*/
public static void registerFunction(String name, FreeRefFunction func){
AnalysisToolPak.registerFunction(name, func);
}
/**
* Register a function in runtime.
*
* @param name the function name
* @param func the functoin to register
* @throws IllegalArgumentException if the function is unknown or already registered.
* @since 3.8 beta6
*/
public static void registerFunction(String name, Function func){
FunctionEval.registerFunction(name, func);
}
}

36
src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
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@ -10,10 +10,8 @@
package org.apache.poi.ss.formula.atp;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import org.apache.poi.ss.formula.OperationEvaluationContext;
import org.apache.poi.ss.formula.eval.NotImplementedException;
import org.apache.poi.ss.formula.eval.ValueEval;
import org.apache.poi.ss.formula.function.FunctionMetadata;
import org.apache.poi.ss.formula.function.FunctionMetadataRegistry;
@ -22,8 +20,8 @@ import org.apache.poi.ss.formula.functions.Function;
import org.apache.poi.ss.formula.functions.NotImplementedFunction;
import org.apache.poi.ss.formula.functions.Sumifs;
import org.apache.poi.ss.formula.udf.UDFFinder;
import org.apache.poi.ss.formula.OperationEvaluationContext;
import org.apache.poi.ss.formula.eval.NotImplementedException;
import java.util.*;
/**
* @author Josh Micich
@ -187,21 +185,39 @@ public final class AnalysisToolPak implements UDFFinder {
}
/**
* Returns an array of function names implemented by POI.
* Returns a collection of ATP function names implemented by POI.
*
* @return an array of supported functions
* @since 3.8 beta6
*/
public static String[] getSupportedFunctionNames(){
public static Collection<String> getSupportedFunctionNames(){
AnalysisToolPak inst = (AnalysisToolPak)instance;
ArrayList<String> lst = new ArrayList<String>();
Collection<String> lst = new TreeSet<String>();
for(String name : inst._functionsByName.keySet()){
FreeRefFunction func = inst._functionsByName.get(name);
if(func != null && !(func instanceof NotImplemented)){
lst.add(name);
}
}
return lst.toArray(new String[lst.size()]);
return Collections.unmodifiableCollection(lst);
}
/**
* Returns a collection of ATP function names NOT implemented by POI.
*
* @return an array of not supported functions
* @since 3.8 beta6
*/
public static Collection<String> getNotSupportedFunctionNames(){
AnalysisToolPak inst = (AnalysisToolPak)instance;
Collection<String> lst = new TreeSet<String>();
for(String name : inst._functionsByName.keySet()){
FreeRefFunction func = inst._functionsByName.get(name);
if(func != null && (func instanceof NotImplemented)){
lst.add(name);
}
}
return Collections.unmodifiableCollection(lst);
}
/**

32
src/java/org/apache/poi/ss/formula/eval/FunctionEval.java
View File

@ -22,7 +22,9 @@ import org.apache.poi.ss.formula.function.FunctionMetadata;
import org.apache.poi.ss.formula.function.FunctionMetadataRegistry;
import org.apache.poi.ss.formula.functions.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.TreeSet;
/**
* @author Amol S. Deshmukh &lt; amolweb at ya hoo dot com &gt;
@ -288,20 +290,40 @@ public final class FunctionEval {
}
/**
* Returns an array of function names implemented by POI.
* Returns a collection of function names implemented by POI.
*
* @return an array of supported functions
* @since 3.8 beta6
*/
public static String[] getSupportedFunctionNames(){
ArrayList<String> lst = new ArrayList<String>();
public static Collection<String> getSupportedFunctionNames(){
Collection<String> lst = new TreeSet<String>();
for(int i = 0; i < functions.length; i++){
Function func = functions[i];
FunctionMetadata metaData = FunctionMetadataRegistry.getFunctionByIndex(i);
if(func != null && !(func instanceof NotImplementedFunction)){
lst.add(metaData.getName());
}
}
lst.add("INDIRECT"); // INDIRECT is a special case
return Collections.unmodifiableCollection(lst);
}
/**
* Returns an array of function names NOT implemented by POI.
*
* @return an array of not supported functions
* @since 3.8 beta6
*/
public static Collection<String> getNotSupportedFunctionNames(){
Collection<String> lst = new TreeSet<String>();
for(int i = 0; i < functions.length; i++){
Function func = functions[i];
if(func != null && (func instanceof NotImplementedFunction)){
FunctionMetadata metaData = FunctionMetadataRegistry.getFunctionByIndex(i);
lst.add(metaData.getName());
}
}
return lst.toArray(new String[lst.size()]);
lst.remove("INDIRECT"); // INDIRECT is a special case
return Collections.unmodifiableCollection(lst);
}
}