diff --git a/CHANGELOG.md b/CHANGELOG.md
index b1e0ae98..91f6adc7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,7 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### BREAKING CHANGE
 
-- Introduction of namespaces for all classes, eg: `PHPExcel_Calculation_Function` becomes `PhpOffice\PhpSpreadsheet\Calculation\Functions`
+- Introduction of namespaces for all classes, eg: `PHPExcel_Calculation_Functions` becomes `PhpOffice\PhpSpreadsheet\Calculation\Functions`
 - Some classes were renamed for clarity and/or consistency:
 
 For a comprehensive list of all class changes, and a semi-automated migration path, read the [migration guide](./docs/Migration-from-PHPExcel.md).
diff --git a/samples/13_Calculation.php b/samples/13_Calculation.php
index 2d087b41..d620a6f2 100644
--- a/samples/13_Calculation.php
+++ b/samples/13_Calculation.php
@@ -7,7 +7,7 @@ require __DIR__ . '/Header.php';
 // List functions
 $helper->log('List implemented functions');
 $calc = \PhpOffice\PhpSpreadsheet\Calculation::getInstance();
-print_r($calc->listFunctionNames());
+print_r($calc->getImplementedFunctionNames());
 
 // Create new Spreadsheet object
 $helper->log('Create new Spreadsheet object');
diff --git a/samples/18_Extendedcalculation.php b/samples/18_Extendedcalculation.php
index a12c5c60..b7d45b33 100644
--- a/samples/18_Extendedcalculation.php
+++ b/samples/18_Extendedcalculation.php
@@ -6,7 +6,7 @@ require __DIR__ . '/Header.php';
 // List functions
 $helper->log('List implemented functions');
 $calc = \PhpOffice\PhpSpreadsheet\Calculation::getInstance();
-print_r($calc->listFunctionNames());
+print_r($calc->getImplementedFunctionNames());
 
 // Create new Spreadsheet object
 $helper->log('Create new Spreadsheet object');
diff --git a/src/PhpSpreadsheet/Calculation.php b/src/PhpSpreadsheet/Calculation.php
index 223b6f13..c9b17374 100644
--- a/src/PhpSpreadsheet/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation.php
@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheet;
 
+use PhpOffice\PhpSpreadsheet\Calculation\Category;
+
 if (!defined('CALCULATION_REGEXP_CELLREF')) {
     //    Test for support of \P (multibyte options) in PCRE
     if (defined('PREG_BAD_UTF8_ERROR')) {
@@ -232,1783 +234,1783 @@ class Calculation
     // PhpSpreadsheet functions
     private static $phpSpreadsheetFunctions = [
         'ABS' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'abs',
             'argumentCount' => '1',
         ],
         'ACCRINT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::ACCRINT',
             'argumentCount' => '4-7',
         ],
         'ACCRINTM' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::ACCRINTM',
             'argumentCount' => '3-5',
         ],
         'ACOS' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'acos',
             'argumentCount' => '1',
         ],
         'ACOSH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'acosh',
             'argumentCount' => '1',
         ],
         'ADDRESS' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::cellAddress',
             'argumentCount' => '2-5',
         ],
         'AMORDEGRC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::AMORDEGRC',
             'argumentCount' => '6,7',
         ],
         'AMORLINC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::AMORLINC',
             'argumentCount' => '6,7',
         ],
         'AND' => [
-            'category' => Calculation\Categories::CATEGORY_LOGICAL,
+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::logicalAnd',
             'argumentCount' => '1+',
         ],
         'AREAS' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'ASC' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'ASIN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'asin',
             'argumentCount' => '1',
         ],
         'ASINH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'asinh',
             'argumentCount' => '1',
         ],
         'ATAN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'atan',
             'argumentCount' => '1',
         ],
         'ATAN2' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::ATAN2',
             'argumentCount' => '2',
         ],
         'ATANH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'atanh',
             'argumentCount' => '1',
         ],
         'AVEDEV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::AVEDEV',
             'argumentCount' => '1+',
         ],
         'AVERAGE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::AVERAGE',
             'argumentCount' => '1+',
         ],
         'AVERAGEA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::AVERAGEA',
             'argumentCount' => '1+',
         ],
         'AVERAGEIF' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::AVERAGEIF',
             'argumentCount' => '2,3',
         ],
         'AVERAGEIFS' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '3+',
         ],
         'BAHTTEXT' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'BESSELI' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BESSELI',
             'argumentCount' => '2',
         ],
         'BESSELJ' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BESSELJ',
             'argumentCount' => '2',
         ],
         'BESSELK' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BESSELK',
             'argumentCount' => '2',
         ],
         'BESSELY' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BESSELY',
             'argumentCount' => '2',
         ],
         'BETADIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::BETADIST',
             'argumentCount' => '3-5',
         ],
         'BETAINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::BETAINV',
             'argumentCount' => '3-5',
         ],
         'BIN2DEC' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BINTODEC',
             'argumentCount' => '1',
         ],
         'BIN2HEX' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BINTOHEX',
             'argumentCount' => '1,2',
         ],
         'BIN2OCT' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::BINTOOCT',
             'argumentCount' => '1,2',
         ],
         'BINOMDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::BINOMDIST',
             'argumentCount' => '4',
         ],
         'CEILING' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::CEILING',
             'argumentCount' => '2',
         ],
         'CELL' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1,2',
         ],
         'CHAR' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::CHARACTER',
             'argumentCount' => '1',
         ],
         'CHIDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CHIDIST',
             'argumentCount' => '2',
         ],
         'CHIINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CHIINV',
             'argumentCount' => '2',
         ],
         'CHITEST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'CHOOSE' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::CHOOSE',
             'argumentCount' => '2+',
         ],
         'CLEAN' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::TRIMNONPRINTABLE',
             'argumentCount' => '1',
         ],
         'CODE' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::ASCIICODE',
             'argumentCount' => '1',
         ],
         'COLUMN' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::COLUMN',
             'argumentCount' => '-1',
             'passByReference' => [true],
         ],
         'COLUMNS' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::COLUMNS',
             'argumentCount' => '1',
         ],
         'COMBIN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::COMBIN',
             'argumentCount' => '2',
         ],
         'COMPLEX' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::COMPLEX',
             'argumentCount' => '2,3',
         ],
         'CONCATENATE' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::CONCATENATE',
             'argumentCount' => '1+',
         ],
         'CONFIDENCE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CONFIDENCE',
             'argumentCount' => '3',
         ],
         'CONVERT' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::CONVERTUOM',
             'argumentCount' => '3',
         ],
         'CORREL' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CORREL',
             'argumentCount' => '2',
         ],
         'COS' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'cos',
             'argumentCount' => '1',
         ],
         'COSH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'cosh',
             'argumentCount' => '1',
         ],
         'COUNT' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::COUNT',
             'argumentCount' => '1+',
         ],
         'COUNTA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::COUNTA',
             'argumentCount' => '1+',
         ],
         'COUNTBLANK' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::COUNTBLANK',
             'argumentCount' => '1',
         ],
         'COUNTIF' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::COUNTIF',
             'argumentCount' => '2',
         ],
         'COUNTIFS' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'COUPDAYBS' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPDAYBS',
             'argumentCount' => '3,4',
         ],
         'COUPDAYS' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPDAYS',
             'argumentCount' => '3,4',
         ],
         'COUPDAYSNC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPDAYSNC',
             'argumentCount' => '3,4',
         ],
         'COUPNCD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPNCD',
             'argumentCount' => '3,4',
         ],
         'COUPNUM' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPNUM',
             'argumentCount' => '3,4',
         ],
         'COUPPCD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::COUPPCD',
             'argumentCount' => '3,4',
         ],
         'COVAR' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::COVAR',
             'argumentCount' => '2',
         ],
         'CRITBINOM' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CRITBINOM',
             'argumentCount' => '3',
         ],
         'CUBEKPIMEMBER' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBEMEMBER' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBEMEMBERPROPERTY' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBERANKEDMEMBER' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBESET' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBESETCOUNT' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUBEVALUE' => [
-            'category' => Calculation\Categories::CATEGORY_CUBE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_CUBE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '?',
         ],
         'CUMIPMT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::CUMIPMT',
             'argumentCount' => '6',
         ],
         'CUMPRINC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::CUMPRINC',
             'argumentCount' => '6',
         ],
         'DATE' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DATE',
             'argumentCount' => '3',
         ],
         'DATEDIF' => [
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+            'category' => Category::CATEGORY_DATE_AND_TIME,
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             'argumentCount' => '2,3',
         ],
         'DATEVALUE' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DATEVALUE',
             'argumentCount' => '1',
         ],
         'DAVERAGE' => [
-            'category' => Calculation\Categories::CATEGORY_DATABASE,
+            'category' => Category::CATEGORY_DATABASE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Database::DAVERAGE',
             'argumentCount' => '3',
         ],
         'DAY' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DAYOFMONTH',
             'argumentCount' => '1',
         ],
         'DAYS360' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DAYS360',
             'argumentCount' => '2,3',
         ],
         'DB' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::DB',
             'argumentCount' => '4,5',
         ],
         'DCOUNT' => [
-            'category' => Calculation\Categories::CATEGORY_DATABASE,
+            'category' => Category::CATEGORY_DATABASE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Database::DCOUNT',
             'argumentCount' => '3',
         ],
         'DCOUNTA' => [
-            'category' => Calculation\Categories::CATEGORY_DATABASE,
+            'category' => Category::CATEGORY_DATABASE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Database::DCOUNTA',
             'argumentCount' => '3',
         ],
         'DDB' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '4,5',
         ],
         'DEC2BIN' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::DECTOBIN',
             'argumentCount' => '1,2',
         ],
         'DEC2HEX' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::DECTOHEX',
             'argumentCount' => '1,2',
         ],
         'DEC2OCT' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::DECTOOCT',
             'argumentCount' => '1,2',
         ],
         'DEGREES' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'rad2deg',
             'argumentCount' => '1',
         ],
         'DELTA' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::DELTA',
             'argumentCount' => '1,2',
         ],
         'DEVSQ' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::DEVSQ',
             'argumentCount' => '1+',
         ],
         'DGET' => [
-            'category' => Calculation\Categories::CATEGORY_DATABASE,
+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DISC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '4,5',
         ],
         'DMAX' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DMIN' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DOLLAR' => [
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+            'category' => Category::CATEGORY_TEXT_AND_DATA,
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             'argumentCount' => '1,2',
         ],
         'DOLLARDE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '2',
         ],
         'DOLLARFR' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::DOLLARFR',
             'argumentCount' => '2',
         ],
         'DPRODUCT' => [
-            'category' => Calculation\Categories::CATEGORY_DATABASE,
+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DSTDEV' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DSTDEVP' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DSUM' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DURATION' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '5,6',
         ],
         'DVAR' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
         'DVARP' => [
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+            'category' => Category::CATEGORY_DATABASE,
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             'argumentCount' => '3',
         ],
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+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::EDATE',
             'argumentCount' => '2',
         ],
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+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '2',
         ],
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+            'category' => Category::CATEGORY_DATE_AND_TIME,
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             'argumentCount' => '2',
         ],
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+            'category' => Category::CATEGORY_ENGINEERING,
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             'argumentCount' => '1,2',
         ],
         'ERFC' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
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             'argumentCount' => '1',
         ],
         'ERROR.TYPE' => [
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-            'functionCall' => 'Calculation\Categories::errorType',
+            'category' => Category::CATEGORY_INFORMATION,
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             'argumentCount' => '1',
         ],
         'EVEN' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1',
         ],
         'EXACT' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'EXP' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'exp',
             'argumentCount' => '1',
         ],
         'EXPONDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::EXPONDIST',
             'argumentCount' => '3',
         ],
         'FACT' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1',
         ],
         'FACTDOUBLE' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1',
         ],
         'FALSE' => [
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+            'category' => Category::CATEGORY_LOGICAL,
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             'argumentCount' => '0',
         ],
         'FDIST' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '3',
         ],
         'FIND' => [
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+            'category' => Category::CATEGORY_TEXT_AND_DATA,
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             'argumentCount' => '2,3',
         ],
         'FINDB' => [
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+            'category' => Category::CATEGORY_TEXT_AND_DATA,
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         ],
         'FINV' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '3',
         ],
         'FISHER' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::FISHER',
             'argumentCount' => '1',
         ],
         'FISHERINV' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '1',
         ],
         'FIXED' => [
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+            'category' => Category::CATEGORY_TEXT_AND_DATA,
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             'argumentCount' => '1-3',
         ],
         'FLOOR' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '2',
         ],
         'FORECAST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '3',
         ],
         'FREQUENCY' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'FTEST' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'FV' => [
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+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '3-5',
         ],
         'FVSCHEDULE' => [
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+            'category' => Category::CATEGORY_FINANCIAL,
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             'argumentCount' => '2',
         ],
         'GAMMADIST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '4',
         ],
         'GAMMAINV' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::GAMMAINV',
             'argumentCount' => '3',
         ],
         'GAMMALN' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::GAMMALN',
             'argumentCount' => '1',
         ],
         'GCD' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1+',
         ],
         'GEOMEAN' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '1+',
         ],
         'GESTEP' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
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             'argumentCount' => '1,2',
         ],
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2+',
         ],
         'GROWTH' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '1-4',
         ],
         'HARMEAN' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::HARMEAN',
             'argumentCount' => '1+',
         ],
         'HEX2BIN' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
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             'argumentCount' => '1,2',
         ],
         'HEX2DEC' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
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             'argumentCount' => '1',
         ],
         'HEX2OCT' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::HEXTOOCT',
             'argumentCount' => '1,2',
         ],
         'HLOOKUP' => [
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+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
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             'argumentCount' => '3,4',
         ],
         'HOUR' => [
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+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::HOUROFDAY',
             'argumentCount' => '1',
         ],
         'HYPERLINK' => [
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+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
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             'argumentCount' => '1,2',
             'passCellReference' => true,
         ],
         'HYPGEOMDIST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::HYPGEOMDIST',
             'argumentCount' => '4',
         ],
         'IF' => [
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+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::statementIf',
             'argumentCount' => '1-3',
         ],
         'IFERROR' => [
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+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::IFERROR',
             'argumentCount' => '2',
         ],
         'IMABS' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMABS',
             'argumentCount' => '1',
         ],
         'IMAGINARY' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMAGINARY',
             'argumentCount' => '1',
         ],
         'IMARGUMENT' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMARGUMENT',
             'argumentCount' => '1',
         ],
         'IMCONJUGATE' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMCONJUGATE',
             'argumentCount' => '1',
         ],
         'IMCOS' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMCOS',
             'argumentCount' => '1',
         ],
         'IMDIV' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMDIV',
             'argumentCount' => '2',
         ],
         'IMEXP' => [
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+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMEXP',
             'argumentCount' => '1',
         ],
         'IMLN' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMLN',
             'argumentCount' => '1',
         ],
         'IMLOG10' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMLOG10',
             'argumentCount' => '1',
         ],
         'IMLOG2' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMLOG2',
             'argumentCount' => '1',
         ],
         'IMPOWER' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMPOWER',
             'argumentCount' => '2',
         ],
         'IMPRODUCT' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMPRODUCT',
             'argumentCount' => '1+',
         ],
         'IMREAL' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMREAL',
             'argumentCount' => '1',
         ],
         'IMSIN' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMSIN',
             'argumentCount' => '1',
         ],
         'IMSQRT' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMSQRT',
             'argumentCount' => '1',
         ],
         'IMSUB' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMSUB',
             'argumentCount' => '2',
         ],
         'IMSUM' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::IMSUM',
             'argumentCount' => '1+',
         ],
         'INDEX' => [
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+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::INDEX',
             'argumentCount' => '1-4',
         ],
         'INDIRECT' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::INDIRECT',
             'argumentCount' => '1,2',
             'passCellReference' => true,
         ],
         'INFO' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'INT' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::INT',
             'argumentCount' => '1',
         ],
         'INTERCEPT' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::INTERCEPT',
             'argumentCount' => '2',
         ],
         'INTRATE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::INTRATE',
             'argumentCount' => '4,5',
         ],
         'IPMT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::IPMT',
             'argumentCount' => '4-6',
         ],
         'IRR' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::IRR',
             'argumentCount' => '1,2',
         ],
         'ISBLANK' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isBlank',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isBlank',
             'argumentCount' => '1',
         ],
         'ISERR' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::IS_ERR',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isErr',
             'argumentCount' => '1',
         ],
         'ISERROR' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::IS_ERROR',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isError',
             'argumentCount' => '1',
         ],
         'ISEVEN' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isEven',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isEven',
             'argumentCount' => '1',
         ],
         'ISLOGICAL' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isLogical',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isLogical',
             'argumentCount' => '1',
         ],
         'ISNA' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isNa',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isNa',
             'argumentCount' => '1',
         ],
         'ISNONTEXT' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isNonText',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isNonText',
             'argumentCount' => '1',
         ],
         'ISNUMBER' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isNumber',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isNumber',
             'argumentCount' => '1',
         ],
         'ISODD' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isOdd',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isOdd',
             'argumentCount' => '1',
         ],
         'ISPMT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::ISPMT',
             'argumentCount' => '4',
         ],
         'ISREF' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'ISTEXT' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::isText',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::isText',
             'argumentCount' => '1',
         ],
         'JIS' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'KURT' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::KURT',
             'argumentCount' => '1+',
         ],
         'LARGE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::LARGE',
             'argumentCount' => '2',
         ],
         'LCM' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1+',
         ],
         'LEFT' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::LEFT',
             'argumentCount' => '1,2',
         ],
         'LEFTB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::LEFT',
             'argumentCount' => '1,2',
         ],
         'LEN' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::STRINGLENGTH',
             'argumentCount' => '1',
         ],
         'LENB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::STRINGLENGTH',
             'argumentCount' => '1',
         ],
         'LINEST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::LINEST',
             'argumentCount' => '1-4',
         ],
         'LN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'log',
             'argumentCount' => '1',
         ],
         'LOG' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1,2',
         ],
         'LOG10' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'log10',
             'argumentCount' => '1',
         ],
         'LOGEST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::LOGEST',
             'argumentCount' => '1-4',
         ],
         'LOGINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
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             'argumentCount' => '3',
         ],
         'LOGNORMDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::LOGNORMDIST',
             'argumentCount' => '3',
         ],
         'LOOKUP' => [
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+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::LOOKUP',
             'argumentCount' => '2,3',
         ],
         'LOWER' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::LOWERCASE',
             'argumentCount' => '1',
         ],
         'MATCH' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::MATCH',
             'argumentCount' => '2,3',
         ],
         'MAX' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MAX',
             'argumentCount' => '1+',
         ],
         'MAXA' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MAXA',
             'argumentCount' => '1+',
         ],
         'MAXIF' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MAXIF',
             'argumentCount' => '2+',
         ],
         'MDETERM' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::MDETERM',
             'argumentCount' => '1',
         ],
         'MDURATION' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '5,6',
         ],
         'MEDIAN' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MEDIAN',
             'argumentCount' => '1+',
         ],
         'MEDIANIF' => [
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-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2+',
         ],
         'MID' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::MID',
             'argumentCount' => '3',
         ],
         'MIDB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::MID',
             'argumentCount' => '3',
         ],
         'MIN' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MIN',
             'argumentCount' => '1+',
         ],
         'MINA' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MINA',
             'argumentCount' => '1+',
         ],
         'MINIF' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MINIF',
             'argumentCount' => '2+',
         ],
         'MINUTE' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::MINUTE',
             'argumentCount' => '1',
         ],
         'MINVERSE' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::MINVERSE',
             'argumentCount' => '1',
         ],
         'MIRR' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::MIRR',
             'argumentCount' => '3',
         ],
         'MMULT' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::MMULT',
             'argumentCount' => '2',
         ],
         'MOD' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::MOD',
             'argumentCount' => '2',
         ],
         'MODE' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::MODE',
             'argumentCount' => '1+',
         ],
         'MONTH' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::MONTHOFYEAR',
             'argumentCount' => '1',
         ],
         'MROUND' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::MROUND',
             'argumentCount' => '2',
         ],
         'MULTINOMIAL' => [
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+            'category' => Category::CATEGORY_MATH_AND_TRIG,
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             'argumentCount' => '1+',
         ],
         'N' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::N',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::n',
             'argumentCount' => '1',
         ],
         'NA' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::NA',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::NA',
             'argumentCount' => '0',
         ],
         'NEGBINOMDIST' => [
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+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::NEGBINOMDIST',
             'argumentCount' => '3',
         ],
         'NETWORKDAYS' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::NETWORKDAYS',
             'argumentCount' => '2+',
         ],
         'NOMINAL' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::NOMINAL',
             'argumentCount' => '2',
         ],
         'NORMDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::NORMDIST',
             'argumentCount' => '4',
         ],
         'NORMINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::NORMINV',
             'argumentCount' => '3',
         ],
         'NORMSDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::NORMSDIST',
             'argumentCount' => '1',
         ],
         'NORMSINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::NORMSINV',
             'argumentCount' => '1',
         ],
         'NOT' => [
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+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::NOT',
             'argumentCount' => '1',
         ],
         'NOW' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DATETIMENOW',
             'argumentCount' => '0',
         ],
         'NPER' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::NPER',
             'argumentCount' => '3-5',
         ],
         'NPV' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::NPV',
             'argumentCount' => '2+',
         ],
         'OCT2BIN' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::OCTTOBIN',
             'argumentCount' => '1,2',
         ],
         'OCT2DEC' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::OCTTODEC',
             'argumentCount' => '1',
         ],
         'OCT2HEX' => [
-            'category' => Calculation\Categories::CATEGORY_ENGINEERING,
+            'category' => Category::CATEGORY_ENGINEERING,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering::OCTTOHEX',
             'argumentCount' => '1,2',
         ],
         'ODD' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::ODD',
             'argumentCount' => '1',
         ],
         'ODDFPRICE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '8,9',
         ],
         'ODDFYIELD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '8,9',
         ],
         'ODDLPRICE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '7,8',
         ],
         'ODDLYIELD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '7,8',
         ],
         'OFFSET' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::OFFSET',
             'argumentCount' => '3-5',
             'passCellReference' => true,
             'passByReference' => [true],
         ],
         'OR' => [
-            'category' => Calculation\Categories::CATEGORY_LOGICAL,
+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::logicalOr',
             'argumentCount' => '1+',
         ],
         'PEARSON' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::CORREL',
             'argumentCount' => '2',
         ],
         'PERCENTILE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::PERCENTILE',
             'argumentCount' => '2',
         ],
         'PERCENTRANK' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::PERCENTRANK',
             'argumentCount' => '2,3',
         ],
         'PERMUT' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::PERMUT',
             'argumentCount' => '2',
         ],
         'PHONETIC' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1',
         ],
         'PI' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'pi',
             'argumentCount' => '0',
         ],
         'PMT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PMT',
             'argumentCount' => '3-5',
         ],
         'POISSON' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::POISSON',
             'argumentCount' => '3',
         ],
         'POWER' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::POWER',
             'argumentCount' => '2',
         ],
         'PPMT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PPMT',
             'argumentCount' => '4-6',
         ],
         'PRICE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PRICE',
             'argumentCount' => '6,7',
         ],
         'PRICEDISC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PRICEDISC',
             'argumentCount' => '4,5',
         ],
         'PRICEMAT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PRICEMAT',
             'argumentCount' => '5,6',
         ],
         'PROB' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '3,4',
         ],
         'PRODUCT' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::PRODUCT',
             'argumentCount' => '1+',
         ],
         'PROPER' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::PROPERCASE',
             'argumentCount' => '1',
         ],
         'PV' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::PV',
             'argumentCount' => '3-5',
         ],
         'QUARTILE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::QUARTILE',
             'argumentCount' => '2',
         ],
         'QUOTIENT' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::QUOTIENT',
             'argumentCount' => '2',
         ],
         'RADIANS' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'deg2rad',
             'argumentCount' => '1',
         ],
         'RAND' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::RAND',
             'argumentCount' => '0',
         ],
         'RANDBETWEEN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::RAND',
             'argumentCount' => '2',
         ],
         'RANK' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::RANK',
             'argumentCount' => '2,3',
         ],
         'RATE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::RATE',
             'argumentCount' => '3-6',
         ],
         'RECEIVED' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::RECEIVED',
             'argumentCount' => '4-5',
         ],
         'REPLACE' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::REPLACE',
             'argumentCount' => '4',
         ],
         'REPLACEB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::REPLACE',
             'argumentCount' => '4',
         ],
         'REPT' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => 'str_repeat',
             'argumentCount' => '2',
         ],
         'RIGHT' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::RIGHT',
             'argumentCount' => '1,2',
         ],
         'RIGHTB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::RIGHT',
             'argumentCount' => '1,2',
         ],
         'ROMAN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::ROMAN',
             'argumentCount' => '1,2',
         ],
         'ROUND' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'round',
             'argumentCount' => '2',
         ],
         'ROUNDDOWN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::ROUNDDOWN',
             'argumentCount' => '2',
         ],
         'ROUNDUP' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::ROUNDUP',
             'argumentCount' => '2',
         ],
         'ROW' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::ROW',
             'argumentCount' => '-1',
             'passByReference' => [true],
         ],
         'ROWS' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::ROWS',
             'argumentCount' => '1',
         ],
         'RSQ' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::RSQ',
             'argumentCount' => '2',
         ],
         'RTD' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '1+',
         ],
         'SEARCH' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::SEARCHINSENSITIVE',
             'argumentCount' => '2,3',
         ],
         'SEARCHB' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::SEARCHINSENSITIVE',
             'argumentCount' => '2,3',
         ],
         'SECOND' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::SECOND',
             'argumentCount' => '1',
         ],
         'SERIESSUM' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SERIESSUM',
             'argumentCount' => '4',
         ],
         'SIGN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SIGN',
             'argumentCount' => '1',
         ],
         'SIN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'sin',
             'argumentCount' => '1',
         ],
         'SINH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'sinh',
             'argumentCount' => '1',
         ],
         'SKEW' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::SKEW',
             'argumentCount' => '1+',
         ],
         'SLN' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::SLN',
             'argumentCount' => '3',
         ],
         'SLOPE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::SLOPE',
             'argumentCount' => '2',
         ],
         'SMALL' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::SMALL',
             'argumentCount' => '2',
         ],
         'SQRT' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'sqrt',
             'argumentCount' => '1',
         ],
         'SQRTPI' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SQRTPI',
             'argumentCount' => '1',
         ],
         'STANDARDIZE' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STANDARDIZE',
             'argumentCount' => '3',
         ],
         'STDEV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STDEV',
             'argumentCount' => '1+',
         ],
         'STDEVA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STDEVA',
             'argumentCount' => '1+',
         ],
         'STDEVP' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STDEVP',
             'argumentCount' => '1+',
         ],
         'STDEVPA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STDEVPA',
             'argumentCount' => '1+',
         ],
         'STEYX' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::STEYX',
             'argumentCount' => '2',
         ],
         'SUBSTITUTE' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::SUBSTITUTE',
             'argumentCount' => '3,4',
         ],
         'SUBTOTAL' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUBTOTAL',
             'argumentCount' => '2+',
         ],
         'SUM' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUM',
             'argumentCount' => '1+',
         ],
         'SUMIF' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMIF',
             'argumentCount' => '2,3',
         ],
         'SUMIFS' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMIFS',
             'argumentCount' => '3+',
         ],
         'SUMPRODUCT' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMPRODUCT',
             'argumentCount' => '1+',
         ],
         'SUMSQ' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMSQ',
             'argumentCount' => '1+',
         ],
         'SUMX2MY2' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMX2MY2',
             'argumentCount' => '2',
         ],
         'SUMX2PY2' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMX2PY2',
             'argumentCount' => '2',
         ],
         'SUMXMY2' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::SUMXMY2',
             'argumentCount' => '2',
         ],
         'SYD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::SYD',
             'argumentCount' => '4',
         ],
         'T' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::RETURNSTRING',
             'argumentCount' => '1',
         ],
         'TAN' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'tan',
             'argumentCount' => '1',
         ],
         'TANH' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => 'tanh',
             'argumentCount' => '1',
         ],
         'TBILLEQ' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::TBILLEQ',
             'argumentCount' => '3',
         ],
         'TBILLPRICE' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::TBILLPRICE',
             'argumentCount' => '3',
         ],
         'TBILLYIELD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::TBILLYIELD',
             'argumentCount' => '3',
         ],
         'TDIST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::TDIST',
             'argumentCount' => '3',
         ],
         'TEXT' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::TEXTFORMAT',
             'argumentCount' => '2',
         ],
         'TIME' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::TIME',
             'argumentCount' => '3',
         ],
         'TIMEVALUE' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::TIMEVALUE',
             'argumentCount' => '1',
         ],
         'TINV' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::TINV',
             'argumentCount' => '2',
         ],
         'TODAY' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::DATENOW',
             'argumentCount' => '0',
         ],
         'TRANSPOSE' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::TRANSPOSE',
             'argumentCount' => '1',
         ],
         'TREND' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::TREND',
             'argumentCount' => '1-4',
         ],
         'TRIM' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::TRIMSPACES',
             'argumentCount' => '1',
         ],
         'TRIMMEAN' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::TRIMMEAN',
             'argumentCount' => '2',
         ],
         'TRUE' => [
-            'category' => Calculation\Categories::CATEGORY_LOGICAL,
+            'category' => Category::CATEGORY_LOGICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Logical::TRUE',
             'argumentCount' => '0',
         ],
         'TRUNC' => [
-            'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\MathTrig::TRUNC',
             'argumentCount' => '1,2',
         ],
         'TTEST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_STATISTICAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '4',
         ],
         'TYPE' => [
-            'category' => Calculation\Categories::CATEGORY_INFORMATION,
-            'functionCall' => 'Calculation\Categories::TYPE',
+            'category' => Category::CATEGORY_INFORMATION,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::TYPE',
             'argumentCount' => '1',
         ],
         'UPPER' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::UPPERCASE',
             'argumentCount' => '1',
         ],
         'USDOLLAR' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '2',
         ],
         'VALUE' => [
-            'category' => Calculation\Categories::CATEGORY_TEXT_AND_DATA,
+            'category' => Category::CATEGORY_TEXT_AND_DATA,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\TextData::VALUE',
             'argumentCount' => '1',
         ],
         'VAR' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::VARFunc',
             'argumentCount' => '1+',
         ],
         'VARA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::VARA',
             'argumentCount' => '1+',
         ],
         'VARP' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::VARP',
             'argumentCount' => '1+',
         ],
         'VARPA' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::VARPA',
             'argumentCount' => '1+',
         ],
         'VDB' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '5-7',
         ],
         'VLOOKUP' => [
-            'category' => Calculation\Categories::CATEGORY_LOOKUP_AND_REFERENCE,
+            'category' => Category::CATEGORY_LOOKUP_AND_REFERENCE,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\LookupRef::VLOOKUP',
             'argumentCount' => '3,4',
         ],
         'WEEKDAY' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::WEEKDAY',
             'argumentCount' => '1,2',
         ],
         'WEEKNUM' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::WEEKNUM',
             'argumentCount' => '1,2',
         ],
         'WEIBULL' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::WEIBULL',
             'argumentCount' => '4',
         ],
         'WORKDAY' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::WORKDAY',
             'argumentCount' => '2+',
         ],
         'XIRR' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::XIRR',
             'argumentCount' => '2,3',
         ],
         'XNPV' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::XNPV',
             'argumentCount' => '3',
         ],
         'YEAR' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::YEAR',
             'argumentCount' => '1',
         ],
         'YEARFRAC' => [
-            'category' => Calculation\Categories::CATEGORY_DATE_AND_TIME,
+            'category' => Category::CATEGORY_DATE_AND_TIME,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime::YEARFRAC',
             'argumentCount' => '2,3',
         ],
         'YIELD' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'category' => Category::CATEGORY_FINANCIAL,
+            'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY',
             'argumentCount' => '6,7',
         ],
         'YIELDDISC' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::YIELDDISC',
             'argumentCount' => '4,5',
         ],
         'YIELDMAT' => [
-            'category' => Calculation\Categories::CATEGORY_FINANCIAL,
+            'category' => Category::CATEGORY_FINANCIAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Financial::YIELDMAT',
             'argumentCount' => '5,6',
         ],
         'ZTEST' => [
-            'category' => Calculation\Categories::CATEGORY_STATISTICAL,
+            'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Statistical::ZTEST',
             'argumentCount' => '2-3',
         ],
@@ -4150,7 +4152,7 @@ class Calculation
     {
         $pFunction = strtoupper($pFunction);
         if (isset(self::$phpSpreadsheetFunctions[$pFunction])) {
-            return self::$phpSpreadsheetFunctions[$pFunction]['functionCall'] != 'Calculation\Categories::DUMMY';
+            return self::$phpSpreadsheetFunctions[$pFunction]['functionCall'] !== '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY';
         } else {
             return false;
         }
@@ -4159,33 +4161,11 @@ class Calculation
     /**
      * Get a list of all implemented functions as an array of function objects
      *
-     * @return    array of Calculation\Categories
+     * @return    array of Calculation\Category
      */
-    public function listFunctions()
+    public function getFunctions()
     {
-        $returnValue = [];
-
-        foreach (self::$phpSpreadsheetFunctions as $functionName => $function) {
-            if ($function['functionCall'] != 'Calculation\Categories::DUMMY') {
-                $returnValue[$functionName] = new Calculation\Categories(
-                    $function['category'],
-                    $functionName,
-                    $function['functionCall']
-                );
-            }
-        }
-
-        return $returnValue;
-    }
-
-    /**
-     * Get a list of all Excel function names
-     *
-     * @return    array
-     */
-    public function listAllFunctionNames()
-    {
-        return array_keys(self::$phpSpreadsheetFunctions);
+        return self::$phpSpreadsheetFunctions;
     }
 
     /**
@@ -4193,11 +4173,11 @@ class Calculation
      *
      * @return    array
      */
-    public function listFunctionNames()
+    public function getImplementedFunctionNames()
     {
         $returnValue = [];
         foreach (self::$phpSpreadsheetFunctions as $functionName => $function) {
-            if ($function['functionCall'] != 'Calculation\Categories::DUMMY') {
+            if ($function['functionCall'] !== '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions::DUMMY') {
                 $returnValue[] = $functionName;
             }
         }
diff --git a/src/PhpSpreadsheet/Calculation/Categories.php b/src/PhpSpreadsheet/Calculation/Categories.php
deleted file mode 100644
index ece83bda..00000000
--- a/src/PhpSpreadsheet/Calculation/Categories.php
+++ /dev/null
@@ -1,145 +0,0 @@
-<?php
-
-namespace PhpOffice\PhpSpreadsheet\Calculation;
-
-/**
- * Copyright (c) 2006 - 2016 PhpSpreadsheet
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- *
- * @category   PhpSpreadsheet
- * @copyright  Copyright (c) 2006 - 2016 PhpSpreadsheet (https://github.com/PHPOffice/PhpSpreadsheet)
- * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
- */
-class Categories
-{
-    /* Function categories */
-    const CATEGORY_CUBE = 'Cube';
-    const CATEGORY_DATABASE = 'Database';
-    const CATEGORY_DATE_AND_TIME = 'Date and Time';
-    const CATEGORY_ENGINEERING = 'Engineering';
-    const CATEGORY_FINANCIAL = 'Financial';
-    const CATEGORY_INFORMATION = 'Information';
-    const CATEGORY_LOGICAL = 'Logical';
-    const CATEGORY_LOOKUP_AND_REFERENCE = 'Lookup and Reference';
-    const CATEGORY_MATH_AND_TRIG = 'Math and Trig';
-    const CATEGORY_STATISTICAL = 'Statistical';
-    const CATEGORY_TEXT_AND_DATA = 'Text and Data';
-
-    /**
-     * Category (represented by CATEGORY_*)
-     *
-     * @var string
-     */
-    private $category;
-
-    /**
-     * Excel function name
-     *
-     * @var string
-     */
-    private $excelName;
-
-    /**
-     * Spreadsheet function name
-     *
-     * @var string
-     */
-    private $spreadsheetName;
-
-    /**
-     * Create a new Categories
-     * @param     string        $pCategory         Category (represented by CATEGORY_*)
-     * @param     string        $pExcelName        Excel function name
-     * @param     string        $spreadsheetName     Spreadsheet internal function name
-     * @throws    Exception
-     */
-    public function __construct($pCategory = null, $pExcelName = null, $spreadsheetName = null)
-    {
-        if (($pCategory !== null) && ($pExcelName !== null) && ($spreadsheetName !== null)) {
-            // Initialise values
-            $this->category = $pCategory;
-            $this->excelName = $pExcelName;
-            $this->spreadsheetName = $spreadsheetName;
-        } else {
-            throw new Exception('Invalid parameters passed.');
-        }
-    }
-
-    /**
-     * Get Category (represented by CATEGORY_*)
-     *
-     * @return string
-     */
-    public function getCategory()
-    {
-        return $this->category;
-    }
-
-    /**
-     * Set Category (represented by CATEGORY_*)
-     *
-     * @param   string        $value
-     * @throws  Exception
-     */
-    public function setCategory($value = null)
-    {
-        if (!is_null($value)) {
-            $this->category = $value;
-        } else {
-            throw new Exception('Invalid parameter passed.');
-        }
-    }
-
-    /**
-     * Get Excel function name
-     *
-     * @return string
-     */
-    public function getExcelName()
-    {
-        return $this->excelName;
-    }
-
-    /**
-     * Set Excel function name
-     *
-     * @param string    $value
-     */
-    public function setExcelName($value)
-    {
-        $this->excelName = $value;
-    }
-
-    /**
-     * Get Spreadsheet function name
-     *
-     * @return string
-     */
-    public function getSpreadsheetName()
-    {
-        return $this->spreadsheetName;
-    }
-
-    /**
-     * Set Spreadsheet function  name
-     *
-     * @param string    $value
-     */
-    public function setSpreadsheetName($value)
-    {
-        $this->spreadsheetName = $value;
-    }
-}
diff --git a/src/PhpSpreadsheet/Calculation/Category.php b/src/PhpSpreadsheet/Calculation/Category.php
new file mode 100644
index 00000000..75a977f2
--- /dev/null
+++ b/src/PhpSpreadsheet/Calculation/Category.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation;
+
+/**
+ * Copyright (c) 2006 - 2016 PhpSpreadsheet
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category   PhpSpreadsheet
+ * @copyright  Copyright (c) 2006 - 2016 PhpSpreadsheet (https://github.com/PHPOffice/PhpSpreadsheet)
+ * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
+ */
+abstract class Category
+{
+    /* Function categories */
+    const CATEGORY_CUBE = 'Cube';
+    const CATEGORY_DATABASE = 'Database';
+    const CATEGORY_DATE_AND_TIME = 'Date and Time';
+    const CATEGORY_ENGINEERING = 'Engineering';
+    const CATEGORY_FINANCIAL = 'Financial';
+    const CATEGORY_INFORMATION = 'Information';
+    const CATEGORY_LOGICAL = 'Logical';
+    const CATEGORY_LOOKUP_AND_REFERENCE = 'Lookup and Reference';
+    const CATEGORY_MATH_AND_TRIG = 'Math and Trig';
+    const CATEGORY_STATISTICAL = 'Statistical';
+    const CATEGORY_TEXT_AND_DATA = 'Text and Data';
+}
diff --git a/src/PhpSpreadsheet/Helper/Migrator.php b/src/PhpSpreadsheet/Helper/Migrator.php
index 289e5640..5fe0f4d5 100644
--- a/src/PhpSpreadsheet/Helper/Migrator.php
+++ b/src/PhpSpreadsheet/Helper/Migrator.php
@@ -100,7 +100,7 @@ class Migrator
             'PHPExcel_CalcEngine_CyclicReferenceStack' => '\\PhpOffice\\PhpSpreadsheet\\CalcEngine\\CyclicReferenceStack',
             'PHPExcel_CalcEngine_Logger' => '\\PhpOffice\\PhpSpreadsheet\\CalcEngine\\Logger',
             'PHPExcel_Calculation_Functions' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Functions',
-            'PHPExcel_Calculation_Function' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Categories',
+            'PHPExcel_Calculation_Function' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Category',
             'PHPExcel_Calculation_Database' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Database',
             'PHPExcel_Calculation_DateTime' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\DateTime',
             'PHPExcel_Calculation_Engineering' => '\\PhpOffice\\PhpSpreadsheet\\Calculation\\Engineering',
diff --git a/tests/PhpSpreadsheetTests/CalculationTest.php b/tests/PhpSpreadsheetTests/CalculationTest.php
index becee1da..603abd4a 100644
--- a/tests/PhpSpreadsheetTests/CalculationTest.php
+++ b/tests/PhpSpreadsheetTests/CalculationTest.php
@@ -30,4 +30,17 @@ class CalculationTest extends \PHPUnit_Framework_TestCase
     {
         return require 'data/CalculationBinaryComparisonOperation.php';
     }
+
+    /**
+     * @dataProvider providerGetFunctions
+     */
+    public function testGetFunctions($category, $functionCall, $argumentCount)
+    {
+        $this->assertTrue(is_callable($functionCall));
+    }
+
+    public function providerGetFunctions()
+    {
+        return Calculation::getInstance()->getFunctions();
+    }
 }