diff --git a/EPPlus.sln b/EPPlus.sln
index a545934..d838aaf 100644
--- a/EPPlus.sln
+++ b/EPPlus.sln
@@ -13,55 +13,26 @@
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NetCoreTests", "NetCoreTests\NetCoreTests.csproj", "{7D59FAA6-A53F-4672-8387-9281731509F2}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EpplusFormulaParser", "EpplusFormulaParser\EpplusFormulaParser.csproj", "{5411F24B-D58C-40F5-9300-E02C28154A4C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
-		Debug|Mixed Platforms = Debug|Mixed Platforms
-		Debug|x86 = Debug|x86
-		Release 4.0|Any CPU = Release 4.0|Any CPU
-		Release 4.0|Mixed Platforms = Release 4.0|Mixed Platforms
-		Release 4.0|x86 = Release 4.0|x86
 		Release|Any CPU = Release|Any CPU
-		Release|Mixed Platforms = Release|Mixed Platforms
-		Release|x86 = Release|x86
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Debug|x86.Build.0 = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|Any CPU.ActiveCfg = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|Any CPU.Build.0 = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|Mixed Platforms.ActiveCfg = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|Mixed Platforms.Build.0 = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|x86.ActiveCfg = Debug|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release 4.0|x86.Build.0 = Debug|Any CPU
 		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|Any CPU.Build.0 = Release|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|Mixed Platforms.Build.0 = Release|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|x86.ActiveCfg = Release|Any CPU
-		{256597F1-67E5-478D-B5B8-3BBB47CB3D3F}.Release|x86.Build.0 = Release|Any CPU
 		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Debug|x86.Build.0 = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|Any CPU.ActiveCfg = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|Any CPU.Build.0 = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|Mixed Platforms.ActiveCfg = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|Mixed Platforms.Build.0 = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|x86.ActiveCfg = Debug|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release 4.0|x86.Build.0 = Debug|Any CPU
 		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|Any CPU.Build.0 = Release|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|Mixed Platforms.Build.0 = Release|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|x86.ActiveCfg = Release|Any CPU
-		{7D59FAA6-A53F-4672-8387-9281731509F2}.Release|x86.Build.0 = Release|Any CPU
+		{5411F24B-D58C-40F5-9300-E02C28154A4C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{5411F24B-D58C-40F5-9300-E02C28154A4C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{5411F24B-D58C-40F5-9300-E02C28154A4C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{5411F24B-D58C-40F5-9300-E02C28154A4C}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
diff --git a/EpplusFormulaParser/EpplusFormulaParser.csproj b/EpplusFormulaParser/EpplusFormulaParser.csproj
new file mode 100644
index 0000000..366cd3d
--- /dev/null
+++ b/EpplusFormulaParser/EpplusFormulaParser.csproj
@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <PackageId>Appsheet.EpplusFormulaParser</PackageId>
+    <Version>1.0.0</Version>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+</Project>
diff --git a/EpplusFormulaParser/Excel/Operators/IOperator.cs b/EpplusFormulaParser/Excel/Operators/IOperator.cs
new file mode 100644
index 0000000..31f9bff
--- /dev/null
+++ b/EpplusFormulaParser/Excel/Operators/IOperator.cs
@@ -0,0 +1,38 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public interface IOperator {
+  OperatorType Type { get; }
+
+  int Precedence { get; }
+}
diff --git a/EpplusFormulaParser/Excel/Operators/Operator.cs b/EpplusFormulaParser/Excel/Operators/Operator.cs
new file mode 100644
index 0000000..f69a12f
--- /dev/null
+++ b/EpplusFormulaParser/Excel/Operators/Operator.cs
@@ -0,0 +1,111 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Frozen;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
+namespace EpplusFormulaParser;
+
+public class Operator : IOperator {
+  private const int _precedencePercent = 2;
+  private const int _precedenceExp = 4;
+  private const int _precedenceMultiplyDivide = 6;
+  private const int _precedenceAddSubtract = 12;
+  private const int _precedenceConcat = 15;
+  private const int _precedenceComparison = 25;
+
+  private Operator(OperatorType type, int precedence) {
+    Type = type;
+    Precedence = precedence;
+  }
+
+  public OperatorType Type { get; }
+
+  public int Precedence { get; }
+
+  public override string ToString() {
+    return "Operator: " + Type;
+  }
+
+  public static IOperator Plus { get; } = new Operator(OperatorType.Plus, _precedenceAddSubtract);
+
+  public static IOperator Minus { get; } = new Operator(OperatorType.Minus, _precedenceAddSubtract);
+
+  public static IOperator Multiply { get; } =
+      new Operator(OperatorType.Multiply, _precedenceMultiplyDivide);
+
+  public static IOperator Divide { get; } =
+      new Operator(OperatorType.Divide, _precedenceMultiplyDivide);
+
+  public static IOperator Exp { get; } = new Operator(OperatorType.Exponentiation, _precedenceExp);
+
+  public static IOperator Concat { get; } = new Operator(OperatorType.Concat, _precedenceConcat);
+
+  public static IOperator GreaterThan { get; } =
+      new Operator(OperatorType.GreaterThan, _precedenceComparison);
+
+  public static IOperator Eq { get; } = new Operator(OperatorType.Equals, _precedenceComparison);
+
+  public static IOperator NotEqualsTo { get; } =
+      new Operator(OperatorType.NotEqualTo, _precedenceComparison);
+
+  public static IOperator GreaterThanOrEqual { get; } =
+      new Operator(OperatorType.GreaterThanOrEqual, _precedenceComparison);
+
+  public static IOperator LessThan { get; } =
+      new Operator(OperatorType.LessThan, _precedenceComparison);
+
+  public static IOperator LessThanOrEqual { get; } =
+      new Operator(OperatorType.LessThanOrEqual, _precedenceComparison);
+
+  public static IOperator Percent { get; } = new Operator(OperatorType.Percent, _precedencePercent);
+
+  private static FrozenDictionary<string, IOperator> _fromString =
+      new Dictionary<string, IOperator> {
+        { "+", Plus },
+        { "-", Minus },
+        { "*", Multiply },
+        { "/", Divide },
+        { "^", Exp },
+        { "=", Eq },
+        { ">", GreaterThan },
+        { ">=", GreaterThanOrEqual },
+        { "<", LessThan },
+        { "<=", LessThanOrEqual },
+        { "<>", NotEqualsTo },
+        { "&", Concat },
+      }.ToFrozenDictionary();
+
+  public static bool TryParse(string opString, [NotNullWhen(true)] out IOperator? @operator) {
+    return _fromString.TryGetValue(opString, out @operator);
+  }
+}
diff --git a/EpplusFormulaParser/Excel/Operators/OperatorType.cs b/EpplusFormulaParser/Excel/Operators/OperatorType.cs
new file mode 100644
index 0000000..13a7dd3
--- /dev/null
+++ b/EpplusFormulaParser/Excel/Operators/OperatorType.cs
@@ -0,0 +1,51 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public enum OperatorType {
+  Undefined,
+  Concat,
+  Plus,
+  Minus,
+  Multiply,
+  Divide,
+  Modulus,
+  Percent,
+  Equals,
+  GreaterThan,
+  GreaterThanOrEqual,
+  LessThan,
+  LessThanOrEqual,
+  NotEqualTo,
+  IntegerDivision,
+  Exponentiation,
+}
diff --git a/EpplusFormulaParser/ExcelUtilities/ExcelAddressBase.cs b/EpplusFormulaParser/ExcelUtilities/ExcelAddressBase.cs
new file mode 100644
index 0000000..a9fe815
--- /dev/null
+++ b/EpplusFormulaParser/ExcelUtilities/ExcelAddressBase.cs
@@ -0,0 +1,206 @@
+using System.Collections.Frozen;
+using System.Collections.Generic;
+using System.Globalization;
+
+/// <summary>
+/// A range address
+/// </summary>
+/// <remarks>Examples of addresses are "A1" "B1:C2" "A:A" "1:1" "A1:E2,G3:G5" </remarks>
+internal static class ExcelAddressUtilities {
+  /// <summary>
+  /// Maximum number of columns in a worksheet (16384).
+  /// </summary>
+  private const int _maxColumns = 16384;
+
+  /// <summary>
+  /// Maximum number of rows in a worksheet (1048576).
+  /// </summary>
+  private const int _maxRows = 1048576;
+
+  private static readonly FrozenSet<char> _formulaChars = new HashSet<char> {
+    '(',
+    ')',
+    '+',
+    '-',
+    '*',
+    '/',
+    '.',
+    '=',
+    '^',
+    '&',
+    '%',
+    '\"',
+  }.ToFrozenSet();
+
+  public enum AddressType {
+    Invalid,
+    InternalAddress,
+    ExternalAddress,
+    InternalName,
+    ExternalName,
+    Formula,
+  }
+
+  public static AddressType IsValid(string address) {
+    if (address == "#REF!") {
+      return AddressType.Invalid;
+    }
+    if (double.TryParse(
+        address,
+        NumberStyles.Any,
+        CultureInfo.InvariantCulture,
+        out _)) //A double, no valid address
+    {
+      return AddressType.Invalid;
+    }
+    if (IsFormula(address)) {
+      return AddressType.Formula;
+    }
+    if (SplitAddress(address, out var wb, out var intAddress)) {
+      if (intAddress.Contains(
+          '[')) //Table reference
+      {
+        return string.IsNullOrEmpty(wb) ? AddressType.InternalAddress : AddressType.ExternalAddress;
+      }
+      if (intAddress.Contains(',')) {
+        intAddress = intAddress[..intAddress.IndexOf(',')];
+      }
+      if (IsAddress(intAddress)) {
+        return string.IsNullOrEmpty(wb) ? AddressType.InternalAddress : AddressType.ExternalAddress;
+      }
+      return string.IsNullOrEmpty(wb) ? AddressType.InternalName : AddressType.ExternalName;
+    }
+    return AddressType.Invalid;
+  }
+
+  private static bool GetRowCol(string address, out int row, out int col, bool throwException) {
+    var colPart = true;
+    var colStartIx = 0;
+    var colLength = 0;
+    col = 0;
+    row = 0;
+
+    if (address.EndsWith("#REF!")) {
+      row = 0;
+      col = 0;
+      return true;
+    }
+
+    var sheetMarkerIndex = address.IndexOf('!');
+    if (sheetMarkerIndex >= 0) {
+      colStartIx = sheetMarkerIndex + 1;
+    }
+    address = address.ToUpper(CultureInfo.InvariantCulture);
+    for (var i = colStartIx; i < address.Length; i++) {
+      var c = address[i];
+      if (colPart && c >= 'A' && c <= 'Z' && colLength <= 3) {
+        col *= 26;
+        col += c - 64;
+        colLength++;
+      } else if (c >= '0' && c <= '9') {
+        row *= 10;
+        row += c - 48;
+        colPart = false;
+      } else if (c == '$') {
+        if (i == colStartIx) {
+          colStartIx++;
+        } else {
+          colPart = false;
+        }
+      } else {
+        row = 0;
+        col = 0;
+        if (throwException) {
+          throw new($"Invalid Address format {address}");
+        }
+        return false;
+      }
+    }
+    return row != 0 || col != 0;
+  }
+
+  private static bool IsAddress(string intAddress) {
+    if (string.IsNullOrEmpty(intAddress)) {
+      return false;
+    }
+    var cells = intAddress.Split(':');
+    int toRow,
+        toCol;
+
+    if (!GetRowCol(cells[0], out var fromRow, out var fromCol, false)) {
+      return false;
+    }
+    if (cells.Length > 1) {
+      if (!GetRowCol(cells[1], out toRow, out toCol, false)) {
+        return false;
+      }
+    } else {
+      toRow = fromRow;
+      toCol = fromCol;
+    }
+    return fromRow <= toRow
+        && fromCol <= toCol
+        && fromCol > -1
+        && toCol <= _maxColumns
+        && fromRow > -1
+        && toRow <= _maxRows;
+  }
+
+  private static bool SplitAddress(string address, out string wb, out string intAddress) {
+    wb = "";
+    intAddress = "";
+    var text = "";
+    var isText = false;
+    var brackPos = -1;
+    for (var i = 0; i < address.Length; i++) {
+      if (address[i] == '\'') {
+        isText = !isText;
+        if (i > 0 && address[i - 1] == '\'') {
+          text += "'";
+        }
+      } else {
+        if (address[i] == '!' && !isText) {
+          if (text.Length > 0 && text[0] == '[') {
+            wb = text.Substring(1, text.IndexOf(']') - 1);
+          }
+          intAddress = address[(i + 1)..];
+          return true;
+        }
+        if (address[i] == '[' && !isText) {
+          if (i
+              > 0) //Table reference return full address;
+          {
+            intAddress = address;
+            return true;
+          }
+          brackPos = i;
+        } else if (address[i] == ']' && !isText) {
+          if (brackPos > -1) {
+            wb = text;
+            text = "";
+          } else {
+            return false;
+          }
+        } else {
+          text += address[i];
+        }
+      }
+    }
+    intAddress = text;
+    return true;
+  }
+
+  private static bool IsFormula(string address) {
+    var isText = false;
+    foreach (var c in address) {
+      if (c == '\'') {
+        isText = !isText;
+      } else {
+        if (isText == false && _formulaChars.Contains(c)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+}
diff --git a/EpplusFormulaParser/Exceptions/ExcelErrorValueException.cs b/EpplusFormulaParser/Exceptions/ExcelErrorValueException.cs
new file mode 100644
index 0000000..a7c9a8e
--- /dev/null
+++ b/EpplusFormulaParser/Exceptions/ExcelErrorValueException.cs
@@ -0,0 +1,5 @@
+﻿using System;
+
+namespace EpplusFormulaParser;
+
+public class ExcelErrorValueException : Exception;
diff --git a/EpplusFormulaParser/Exceptions/UnrecognizedTokenException.cs b/EpplusFormulaParser/Exceptions/UnrecognizedTokenException.cs
new file mode 100644
index 0000000..ce20e84
--- /dev/null
+++ b/EpplusFormulaParser/Exceptions/UnrecognizedTokenException.cs
@@ -0,0 +1,37 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System;
+
+namespace EpplusFormulaParser;
+
+public class UnrecognizedTokenException(Token token)
+    : Exception("Unrecognized token: " + token.Value);
diff --git a/EpplusFormulaParser/ExpressionGraph/AtomicExpression.cs b/EpplusFormulaParser/ExpressionGraph/AtomicExpression.cs
new file mode 100644
index 0000000..4fb567c
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/AtomicExpression.cs
@@ -0,0 +1,36 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public abstract class AtomicExpression(string expression) : Expression(expression) {
+  public override bool IsGroupedExpression => false;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/BooleanExpression.cs b/EpplusFormulaParser/ExpressionGraph/BooleanExpression.cs
new file mode 100644
index 0000000..8cc1146
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/BooleanExpression.cs
@@ -0,0 +1,34 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class BooleanExpression(string expression) : AtomicExpression(expression);
diff --git a/EpplusFormulaParser/ExpressionGraph/ConstantExpressions.cs b/EpplusFormulaParser/ExpressionGraph/ConstantExpressions.cs
new file mode 100644
index 0000000..63b8f23
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ConstantExpressions.cs
@@ -0,0 +1,7 @@
+namespace EpplusFormulaParser;
+
+public static class ConstantExpressions {
+  public static Expression Percent => new ConstantExpression("Percent");
+}
+
+public class ConstantExpression(string title) : AtomicExpression(title);
diff --git a/EpplusFormulaParser/ExpressionGraph/DecimalExpression.cs b/EpplusFormulaParser/ExpressionGraph/DecimalExpression.cs
new file mode 100644
index 0000000..704308b
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/DecimalExpression.cs
@@ -0,0 +1,46 @@
+﻿using System.Globalization;
+
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class DecimalExpression(string expression, bool negate) : AtomicExpression(expression) {
+  public double Compile() {
+    var result = double.Parse(ExpressionString, CultureInfo.InvariantCulture);
+    if (negate) {
+      result = -result;
+    }
+    return result;
+  }
+
+  public bool IsNegated => negate;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/EnumerableExpression.cs b/EpplusFormulaParser/ExpressionGraph/EnumerableExpression.cs
new file mode 100644
index 0000000..29367f1
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/EnumerableExpression.cs
@@ -0,0 +1,36 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class EnumerableExpression : Expression {
+  public override bool IsGroupedExpression => false;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/ExcelAddressExpression.cs b/EpplusFormulaParser/ExpressionGraph/ExcelAddressExpression.cs
new file mode 100644
index 0000000..f58b294
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ExcelAddressExpression.cs
@@ -0,0 +1,38 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class ExcelAddressExpression(string expression, bool negate) : AtomicExpression(expression) {
+  public override bool IsGroupedExpression => false;
+
+  public bool IsNegated => negate;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/ExcelErrorExpression.cs b/EpplusFormulaParser/ExpressionGraph/ExcelErrorExpression.cs
new file mode 100644
index 0000000..95cc139
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ExcelErrorExpression.cs
@@ -0,0 +1,36 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class ExcelErrorExpression(string expression) : Expression(expression) {
+  public override bool IsGroupedExpression => false;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/Expression.cs b/EpplusFormulaParser/ExpressionGraph/Expression.cs
new file mode 100644
index 0000000..506469a
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/Expression.cs
@@ -0,0 +1,78 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace EpplusFormulaParser;
+
+public abstract class Expression {
+  public string ExpressionString { get; private set; }
+
+  private readonly List<Expression> _children;
+
+  public IReadOnlyList<Expression> Children { get; }
+
+  public Expression? Next { get; set; }
+
+  public Expression? Prev { get; set; }
+
+  public IOperator? Operator { get; set; }
+
+  public abstract bool IsGroupedExpression { get; }
+
+  protected Expression()
+      : this("") {}
+
+  protected Expression(string expression) {
+    ExpressionString = expression;
+    _children = [];
+    Children = _children.AsReadOnly();
+  }
+
+  public virtual bool ParentIsLookupFunction { get; set; }
+
+  public virtual bool HasChildren => _children.Count != 0;
+
+  internal virtual Expression PrepareForNextChild() {
+    return this;
+  }
+
+  public virtual Expression AddChild(Expression child) {
+    if (_children.Count != 0) {
+      var last = _children.Last();
+      child.Prev = last;
+      last.Next = child;
+    }
+    _children.Add(child);
+    return child;
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/ExpressionFactory.cs b/EpplusFormulaParser/ExpressionGraph/ExpressionFactory.cs
new file mode 100644
index 0000000..4ce661a
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ExpressionFactory.cs
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+internal static class ExpressionFactory {
+  public static Expression Create(Token token) {
+    switch (token.TokenType) {
+      case TokenType.Integer:
+        return new IntegerExpression(token.Value, token.IsNegated);
+      case TokenType.String:
+        return new StringExpression(token.Value);
+      case TokenType.Decimal:
+        return new DecimalExpression(token.Value, token.IsNegated);
+      case TokenType.Boolean:
+        return new BooleanExpression(token.Value);
+      case TokenType.ExcelAddress:
+        return new ExcelAddressExpression(token.Value, token.IsNegated);
+      case TokenType.InvalidReference:
+        return new ExcelErrorExpression(token.Value);
+      case TokenType.NumericError:
+        return new ExcelErrorExpression(token.Value);
+      case TokenType.ValueDataTypeError:
+        return new ExcelErrorExpression(token.Value);
+      case TokenType.Null:
+        return new ExcelErrorExpression(token.Value);
+      case TokenType.NameValue:
+        return new NamedValueExpression(token.Value);
+      default:
+        return new StringExpression(token.Value);
+    }
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/ExpressionGraph.cs b/EpplusFormulaParser/ExpressionGraph/ExpressionGraph.cs
new file mode 100644
index 0000000..100e186
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ExpressionGraph.cs
@@ -0,0 +1,56 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Generic;
+
+namespace EpplusFormulaParser;
+
+public sealed class ExpressionGraph {
+  private readonly List<Expression> _expressions;
+
+  public IReadOnlyList<Expression> Expressions { get; }
+
+  public Expression? Current { get; private set; }
+
+  internal ExpressionGraph() {
+    _expressions = [];
+    Expressions = _expressions.AsReadOnly();
+  }
+
+  internal void Add(Expression expression) {
+    _expressions.Add(expression);
+    if (Current != null) {
+      Current.Next = expression;
+      expression.Prev = Current;
+    }
+    Current = expression;
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/ExpressionGraphBuilder.cs b/EpplusFormulaParser/ExpressionGraph/ExpressionGraphBuilder.cs
new file mode 100644
index 0000000..6d6b711
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/ExpressionGraphBuilder.cs
@@ -0,0 +1,174 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace EpplusFormulaParser;
+
+internal sealed class ExpressionGraphBuilder {
+  private readonly ExpressionGraph _graph = new();
+  private int _tokenIndex;
+  private bool _negateNextExpression;
+
+  public ExpressionGraph Build(List<Token> tokens) {
+    _tokenIndex = 0;
+    BuildUp(tokens, null);
+    return _graph;
+  }
+
+  private void BuildUp(List<Token> tokens, Expression? parent) {
+    while (_tokenIndex < tokens.Count) {
+      var token = tokens[_tokenIndex];
+      if (token.TokenType == TokenType.Operator && Operator.TryParse(token.Value, out var op)) {
+        SetOperatorOnExpression(parent, op);
+      } else if (token.TokenType == TokenType.Function) {
+        BuildFunctionExpression(tokens, parent, token.Value);
+      } else if (token.TokenType == TokenType.OpeningEnumerable) {
+        _tokenIndex++;
+        BuildEnumerableExpression(tokens, parent);
+      } else if (token.TokenType == TokenType.OpeningParenthesis) {
+        _tokenIndex++;
+        BuildGroupExpression(tokens, parent);
+      } else if (token.TokenType == TokenType.ClosingParenthesis
+          || token.TokenType == TokenType.ClosingEnumerable) {
+        break;
+      } else if (token.TokenType == TokenType.Negator) {
+        _negateNextExpression = true;
+      } else if (token.TokenType == TokenType.Percent) {
+        SetOperatorOnExpression(parent, Operator.Percent);
+        if (parent == null) {
+          _graph.Add(ConstantExpressions.Percent);
+        } else {
+          parent.AddChild(ConstantExpressions.Percent);
+        }
+      } else {
+        CreateAndAppendExpression(ref parent, token);
+      }
+      _tokenIndex++;
+    }
+  }
+
+  private void BuildEnumerableExpression(List<Token> tokens, Expression? parent) {
+    if (parent == null) {
+      _graph.Add(new EnumerableExpression());
+      BuildUp(tokens, _graph.Current);
+    } else {
+      var enumerableExpression = new EnumerableExpression();
+      parent.AddChild(enumerableExpression);
+      BuildUp(tokens, enumerableExpression);
+    }
+  }
+
+  private void CreateAndAppendExpression(ref Expression? parent, Token token) {
+    if (IsWaste(token)) {
+      return;
+    }
+    if (parent != null
+        && (token.TokenType == TokenType.Comma || token.TokenType == TokenType.SemiColon)) {
+      parent = parent.PrepareForNextChild();
+      return;
+    }
+    if (_negateNextExpression) {
+      token.Negate();
+      _negateNextExpression = false;
+    }
+    var expression = ExpressionFactory.Create(token);
+    if (parent == null) {
+      _graph.Add(expression);
+    } else {
+      parent.AddChild(expression);
+    }
+  }
+
+  private bool IsWaste(Token token) {
+    if (token.TokenType == TokenType.String) {
+      return true;
+    }
+    return false;
+  }
+
+  private void BuildFunctionExpression(List<Token> tokens, Expression? parent, string funcName) {
+    if (parent == null) {
+      _graph.Add(new FunctionExpression(funcName));
+      _negateNextExpression = false;
+      HandleFunctionArguments(tokens, _graph.Current!);
+    } else {
+      var func = new FunctionExpression(funcName);
+      _negateNextExpression = false;
+      parent.AddChild(func);
+      HandleFunctionArguments(tokens, func);
+    }
+  }
+
+  private void HandleFunctionArguments(List<Token> tokens, Expression function) {
+    _tokenIndex++;
+    var token = tokens.ElementAt(_tokenIndex);
+    if (token.TokenType != TokenType.OpeningParenthesis) {
+      throw new ExcelErrorValueException();
+    }
+    _tokenIndex++;
+    BuildUp(tokens, function.Children.First());
+  }
+
+  private void BuildGroupExpression(List<Token> tokens, Expression? parent) {
+    if (parent == null) {
+      _graph.Add(new GroupExpression(_negateNextExpression));
+      _negateNextExpression = false;
+      BuildUp(tokens, _graph.Current);
+    } else {
+      if (parent.IsGroupedExpression || parent is FunctionArgumentExpression) {
+        var newGroupExpression = new GroupExpression(_negateNextExpression);
+        _negateNextExpression = false;
+        parent.AddChild(newGroupExpression);
+        BuildUp(tokens, newGroupExpression);
+      }
+      BuildUp(tokens, parent);
+    }
+  }
+
+  private void SetOperatorOnExpression(Expression? parent, IOperator op) {
+    if (parent == null) {
+      _graph.Current!.Operator = op;
+    } else {
+      Expression candidate;
+      if (parent is FunctionArgumentExpression) {
+        candidate = parent.Children.Last();
+      } else {
+        candidate = parent.Children.Last();
+        if (candidate is FunctionArgumentExpression) {
+          candidate = candidate.Children.Last();
+        }
+      }
+      candidate.Operator = op;
+    }
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/FunctionArgumentExpression.cs b/EpplusFormulaParser/ExpressionGraph/FunctionArgumentExpression.cs
new file mode 100644
index 0000000..ab9e322
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/FunctionArgumentExpression.cs
@@ -0,0 +1,50 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public sealed class FunctionArgumentExpression(Expression function) : GroupExpression(false) {
+  public override bool ParentIsLookupFunction {
+    get => base.ParentIsLookupFunction;
+    set {
+      base.ParentIsLookupFunction = value;
+      foreach (var child in Children) {
+        child.ParentIsLookupFunction = value;
+      }
+    }
+  }
+
+  public override bool IsGroupedExpression => false;
+
+  internal override Expression PrepareForNextChild() {
+    return function.PrepareForNextChild();
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/FunctionExpression.cs b/EpplusFormulaParser/ExpressionGraph/FunctionExpression.cs
new file mode 100644
index 0000000..19c5c57
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/FunctionExpression.cs
@@ -0,0 +1,52 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Linq;
+
+namespace EpplusFormulaParser;
+
+public class FunctionExpression : AtomicExpression {
+  public FunctionExpression(string expression)
+      : base(expression) {
+    base.AddChild(new FunctionArgumentExpression(this));
+  }
+
+  internal override Expression PrepareForNextChild() {
+    return base.AddChild(new FunctionArgumentExpression(this));
+  }
+
+  public override bool HasChildren => Children.Any() && Children[0].Children.Any();
+
+  public override Expression AddChild(Expression child) {
+    Children[^1].AddChild(child);
+    return child;
+  }
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/GroupExpression.cs b/EpplusFormulaParser/ExpressionGraph/GroupExpression.cs
new file mode 100644
index 0000000..7f184c0
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/GroupExpression.cs
@@ -0,0 +1,38 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class GroupExpression(bool isNegated) : Expression {
+  public override bool IsGroupedExpression => true;
+
+  public bool IsNegated => isNegated;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/IntegerExpression.cs b/EpplusFormulaParser/ExpressionGraph/IntegerExpression.cs
new file mode 100644
index 0000000..e1f9f7b
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/IntegerExpression.cs
@@ -0,0 +1,46 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Globalization;
+
+namespace EpplusFormulaParser;
+
+public class IntegerExpression(string expression, bool negate) : AtomicExpression(expression) {
+  public double Compile() {
+    var result = double.Parse(ExpressionString, CultureInfo.InvariantCulture);
+    if (negate) {
+      result = -result;
+    }
+    return result;
+  }
+
+  public bool IsNegated => negate;
+}
diff --git a/EpplusFormulaParser/ExpressionGraph/NamedValueExpression.cs b/EpplusFormulaParser/ExpressionGraph/NamedValueExpression.cs
new file mode 100644
index 0000000..c0fee75
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/NamedValueExpression.cs
@@ -0,0 +1,34 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class NamedValueExpression(string expression) : AtomicExpression(expression);
diff --git a/EpplusFormulaParser/ExpressionGraph/StringExpression.cs b/EpplusFormulaParser/ExpressionGraph/StringExpression.cs
new file mode 100644
index 0000000..9d452d8
--- /dev/null
+++ b/EpplusFormulaParser/ExpressionGraph/StringExpression.cs
@@ -0,0 +1,34 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class StringExpression(string expression) : AtomicExpression(expression);
diff --git a/EpplusFormulaParser/FormulaParser.cs b/EpplusFormulaParser/FormulaParser.cs
new file mode 100644
index 0000000..84f2a1e
--- /dev/null
+++ b/EpplusFormulaParser/FormulaParser.cs
@@ -0,0 +1,41 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public static class FormulaParser {
+  public static ExpressionGraph ParseToGraph(string formula) {
+    var tokens = Lexer.Tokenize(formula);
+    var expressionGraphBuilder = new ExpressionGraphBuilder();
+    var graph = expressionGraphBuilder.Build(tokens);
+    return graph;
+  }
+}
diff --git a/EpplusFormulaParser/FunctionRepository.cs b/EpplusFormulaParser/FunctionRepository.cs
new file mode 100644
index 0000000..c096cb8
--- /dev/null
+++ b/EpplusFormulaParser/FunctionRepository.cs
@@ -0,0 +1,192 @@
+/* Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ *******************************************************************************
+ * Mats Alm   		                Added		                2013-12-03
+ *******************************************************************************/
+
+using System;
+using System.Collections.Frozen;
+using System.Collections.Generic;
+
+namespace EpplusFormulaParser;
+
+internal static class FunctionRepository {
+  private static readonly FrozenSet<string> _functions = new HashSet<string>(
+      StringComparer.InvariantCultureIgnoreCase) {
+    // Text
+    "len",
+    "lower",
+    "upper",
+    "left",
+    "right",
+    "mid",
+    "replace",
+    "rept",
+    "substitute",
+    "concatenate",
+    "char",
+    "exact",
+    "find",
+    "fixed",
+    "proper",
+    "text",
+    "t",
+    "hyperlink",
+    // Numbers
+    "int",
+    // Math
+    "abs",
+    "asin",
+    "asinh",
+    "cos",
+    "cosh",
+    "power",
+    "sign",
+    "sqrt",
+    "sqrtpi",
+    "pi",
+    "product",
+    "ceiling",
+    "count",
+    "counta",
+    "countblank",
+    "countif",
+    "countifs",
+    "fact",
+    "floor",
+    "sin",
+    "sinh",
+    "sum",
+    "sumif",
+    "sumifs",
+    "sumproduct",
+    "sumsq",
+    "stdev",
+    "stdevp",
+    "stdev.s",
+    "stdev.p",
+    "subtotal",
+    "exp",
+    "log",
+    "log10",
+    "ln",
+    "max",
+    "maxa",
+    "median",
+    "min",
+    "mina",
+    "mod",
+    "average",
+    "averagea",
+    "averageif",
+    "averageifs",
+    "round",
+    "rounddown",
+    "roundup",
+    "rand",
+    "randbetween",
+    "quotient",
+    "trunc",
+    "tan",
+    "tanh",
+    "atan",
+    "atan2",
+    "atanh",
+    "acos",
+    "acosh",
+    "var",
+    "varp",
+    "large",
+    "small",
+    "degrees",
+    // Information
+    "isblank",
+    "isnumber",
+    "istext",
+    "isnontext",
+    "iserror",
+    "iserr",
+    "error.type",
+    "iseven",
+    "isodd",
+    "islogical",
+    "isna",
+    "na",
+    "n",
+    // Logical
+    "if",
+    "iferror",
+    "ifna",
+    "not",
+    "and",
+    "or",
+    "true",
+    "false",
+    // Reference and lookup
+    "address",
+    "hlookup",
+    "vlookup",
+    "lookup",
+    "match",
+    "row",
+    "rows",
+    "column",
+    "columns",
+    "choose",
+    "index",
+    "indirect",
+    "offset",
+    // Date
+    "date",
+    "today",
+    "now",
+    "day",
+    "month",
+    "year",
+    "time",
+    "hour",
+    "minute",
+    "second",
+    "weeknum",
+    "weekday",
+    "days360",
+    "yearfrac",
+    "edate",
+    "eomonth",
+    "isoweeknum",
+    "workday",
+    // Database
+    "dget",
+    "dcount",
+    "dcounta",
+    "dmax",
+    "dmin",
+    "dsum",
+    "daverage",
+    "dvar",
+    "dvarp",
+  }.ToFrozenSet();
+
+  public static bool IsFunctionName(string name) {
+    return _functions.Contains(name);
+  }
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/Lexer.cs b/EpplusFormulaParser/LexicalAnalysis/Lexer.cs
new file mode 100644
index 0000000..979b42e
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/Lexer.cs
@@ -0,0 +1,42 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Generic;
+
+namespace EpplusFormulaParser;
+
+internal static class Lexer {
+  public static List<Token> Tokenize(string input) {
+    var tokens = SourceCodeTokenizer.Tokenize(input);
+    SyntacticAnalyzer.Analyze(tokens);
+    return tokens;
+  }
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/SourceCodeTokenizer.cs b/EpplusFormulaParser/LexicalAnalysis/SourceCodeTokenizer.cs
new file mode 100644
index 0000000..08c1c37
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/SourceCodeTokenizer.cs
@@ -0,0 +1,269 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Text.RegularExpressions;
+
+namespace EpplusFormulaParser;
+
+internal static partial class SourceCodeTokenizer {
+  public static List<Token> Tokenize(string input) {
+    if (string.IsNullOrEmpty(input)) {
+      return [];
+    }
+    // MA 1401: Ignore leading plus in formula.
+    input = input.TrimStart('+');
+    var context = new TokenizerContext(input);
+
+    var isSingleQuoteString = false;
+    for (var i = 0; i < context.Formula.Length; i++) {
+      var c = context.Formula[i];
+      if (CharIsTokenSeparator(c, out var tokenSeparator)) {
+        if (context.IsInString) {
+          if (IsDoubleQuote(tokenSeparator, i, context)) {
+            i++;
+            context.AppendToCurrentToken(c);
+            continue;
+          }
+          if (tokenSeparator.TokenType != TokenType.String) {
+            context.AppendToCurrentToken(c);
+            continue;
+          }
+          // CHANGE 2
+          if ((isSingleQuoteString && c != '\'') || (!isSingleQuoteString && c != '"')) {
+            context.AppendToCurrentToken(c);
+            continue;
+          }
+        }
+        if (tokenSeparator.TokenType == TokenType.OpeningBracket) {
+          context.AppendToCurrentToken(c);
+          context.BracketCount++;
+          continue;
+        }
+        if (tokenSeparator.TokenType == TokenType.ClosingBracket) {
+          context.AppendToCurrentToken(c);
+          context.BracketCount--;
+          continue;
+        }
+        if (context.BracketCount > 0) {
+          context.AppendToCurrentToken(c);
+          continue;
+        }
+        // two operators in sequence could be "<=" or ">="
+        if (IsPartOfMultipleCharSeparator(context, c)) {
+          var sOp = context.LastToken!.Value + c.ToString(CultureInfo.InvariantCulture);
+          var op = TokenSeparatorProvider.Tokens[sOp];
+          context.ReplaceLastToken(op);
+          context.NewToken();
+          continue;
+        }
+        if (tokenSeparator.TokenType == TokenType.String) {
+          // CHANGE3 :
+          isSingleQuoteString = c == '\'';
+          if (context.LastToken is { TokenType: TokenType.OpeningEnumerable }) {
+            // context.AppendToCurrentToken(c);  // Praveen's change of 10/28/2015
+            context.ToggleIsInString();
+            continue;
+          }
+          if (context.LastToken is { TokenType: TokenType.String }) {
+            context.AddToken(
+                !context.CurrentTokenHasValue
+                    ? new(string.Empty, TokenType.StringContent)
+                    : new Token(context.CurrentToken, TokenType.StringContent));
+          }
+          context.AddToken(new("\"", TokenType.String));
+          context.ToggleIsInString();
+          context.NewToken();
+          continue;
+        }
+        if (context.CurrentTokenHasValue) {
+          if (StringRegex().IsMatch(context.CurrentToken)) {
+            context.AddToken(new(context.CurrentToken, TokenType.StringContent));
+          } else {
+            context.AddToken(CreateToken(context));
+          }
+
+          //If the next token is an opening parantheses and the previous token is interpeted as an address or name, then the current token is a function
+          if (tokenSeparator.TokenType == TokenType.OpeningParenthesis
+              && context.LastToken?.TokenType is TokenType.ExcelAddress or TokenType.NameValue) {
+            context.LastToken.TokenType = TokenType.Function;
+          }
+        }
+        if (tokenSeparator.Value == "-") {
+          if (TokenIsNegator(context)) {
+            context.AddToken(new("-", TokenType.Negator));
+            continue;
+          }
+        }
+        context.AddToken(tokenSeparator);
+        context.NewToken();
+        continue;
+      }
+      context.AppendToCurrentToken(c);
+    }
+    if (context.CurrentTokenHasValue) {
+      context.AddToken(CreateToken(context));
+    }
+
+    CleanupTokens(context);
+
+    return context.Result;
+  }
+
+  private static bool IsDoubleQuote(
+      Token tokenSeparator,
+      int formulaCharIndex,
+      TokenizerContext context) {
+    return tokenSeparator.TokenType == TokenType.String
+        && formulaCharIndex + 1 < context.Formula.Length
+        && context.Formula[formulaCharIndex + 1] == '\"';
+  }
+
+  private static void CleanupTokens(TokenizerContext context) {
+    for (var i = 0; i < context.Result.Count; i++) {
+      var token = context.Result[i];
+      if (token.TokenType == TokenType.Unrecognized) {
+        if (i < context.Result.Count - 1) {
+          if (context.Result[i + 1].TokenType == TokenType.OpeningParenthesis) {
+            token.TokenType = TokenType.Function;
+          } else {
+            token.TokenType = TokenType.NameValue;
+          }
+        } else {
+          token.TokenType = TokenType.NameValue;
+        }
+      } else if (token.TokenType == TokenType.Function) {
+        if (i < context.Result.Count - 1) {
+          if (context.Result[i + 1].TokenType == TokenType.OpeningParenthesis) {
+            token.TokenType = TokenType.Function;
+          } else {
+            token.TokenType = TokenType.Unrecognized;
+          }
+        } else {
+          token.TokenType = TokenType.Unrecognized;
+        }
+      } else if ((token.TokenType == TokenType.Operator || token.TokenType == TokenType.Negator)
+          && i < context.Result.Count - 1
+          && (token.Value == "+" || token.Value == "-")) {
+        if (i > 0
+            && token.Value
+                == "+") //Remove any + with an opening parenthesis before.
+        {
+          if (context.Result[i - 1].TokenType == TokenType.OpeningParenthesis) {
+            context.Result.RemoveAt(i);
+            SetNegatorOperator(context, i);
+            i--;
+            continue;
+          }
+        }
+
+        var nextToken = context.Result[i + 1];
+        if (nextToken.TokenType == TokenType.Operator || nextToken.TokenType == TokenType.Negator) {
+          if (token.Value == "+" && (nextToken.Value == "+" || nextToken.Value == "-")) {
+            //Remove first
+            context.Result.RemoveAt(i);
+            SetNegatorOperator(context, i);
+            i--;
+          } else if (token.Value == "-" && nextToken.Value == "+") {
+            //Remove second
+            context.Result.RemoveAt(i + 1);
+            SetNegatorOperator(context, i);
+            i--;
+          } else if (token.Value == "-" && nextToken.Value == "-") {
+            //Remove first and set operator to +
+            context.Result.RemoveAt(i);
+            if (i == 0) {
+              context.Result.RemoveAt(i + 1);
+              i += 2;
+            } else {
+              //context.Result[i].TokenType = TokenType.Operator;
+              //context.Result[i].Value = "+";
+              context.Result[i] = TokenSeparatorProvider.Tokens["+"];
+              SetNegatorOperator(context, i);
+              i--;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  private static void SetNegatorOperator(TokenizerContext context, int i) {
+    if (context.Result[i].Value == "-"
+        && i > 0
+        && (context.Result[i].TokenType == TokenType.Operator
+                || context.Result[i].TokenType == TokenType.Negator)) {
+      if (TokenIsNegator(context.Result[i - 1])) {
+        context.Result[i] = new("-", TokenType.Negator);
+      } else {
+        context.Result[i] = TokenSeparatorProvider.Tokens["-"];
+      }
+    }
+  }
+
+  private static bool TokenIsNegator(TokenizerContext context) {
+    return TokenIsNegator(context.LastToken);
+  }
+
+  private static bool TokenIsNegator(Token? t) {
+    return t == null
+        || t.TokenType == TokenType.Operator
+        || t.TokenType == TokenType.OpeningParenthesis
+        || t.TokenType == TokenType.Comma
+        || t.TokenType == TokenType.SemiColon
+        || t.TokenType == TokenType.OpeningEnumerable;
+  }
+
+  private static bool IsPartOfMultipleCharSeparator(TokenizerContext context, char c) {
+    var lastToken = context.LastToken != null ? context.LastToken.Value : string.Empty;
+    return TokenSeparatorProvider.IsOperator(lastToken)
+        && TokenSeparatorProvider.IsPossibleLastPartOfMultipleCharOperator(
+            c.ToString(CultureInfo.InvariantCulture))
+        && !context.CurrentTokenHasValue;
+  }
+
+  private static Token CreateToken(TokenizerContext context) {
+    if (context is { CurrentToken: "-", LastToken: null }) {
+      throw new NullReferenceException();
+    }
+    return TokenFactory.Create(context.Result, context.CurrentToken);
+  }
+
+  private static bool CharIsTokenSeparator(char c, [NotNullWhen(true)] out Token? token) {
+    return TokenSeparatorProvider.Tokens.TryGetValue(c.ToString(), out token);
+  }
+
+  [GeneratedRegex("^\"*$")]
+  private static partial Regex StringRegex();
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/SyntacticAnalyzer.cs b/EpplusFormulaParser/LexicalAnalysis/SyntacticAnalyzer.cs
new file mode 100644
index 0000000..2d698b7
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/SyntacticAnalyzer.cs
@@ -0,0 +1,88 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System;
+using System.Collections.Generic;
+
+namespace EpplusFormulaParser;
+
+internal static class SyntacticAnalyzer {
+  private ref struct AnalyzingContext {
+    public int NumberOfOpenedParentheses { get; set; }
+
+    public int NumberOfClosedParentheses { get; set; }
+
+    public int OpenedStrings { get; set; }
+
+    public int ClosedStrings { get; set; }
+
+    public bool IsInString { get; set; }
+  }
+
+  public static void Analyze(IEnumerable<Token> tokens) {
+    var context = new AnalyzingContext();
+    foreach (var token in tokens) {
+      if (token.TokenType == TokenType.Unrecognized) {
+        throw new UnrecognizedTokenException(token);
+      }
+      EnsureParenthesesAreWellFormed(token, ref context);
+      EnsureStringsAreWellFormed(token, ref context);
+    }
+    Validate(ref context);
+  }
+
+  private static void Validate(ref AnalyzingContext context) {
+    if (context.NumberOfOpenedParentheses != context.NumberOfClosedParentheses) {
+      throw new FormatException("Number of opened and closed parentheses does not match");
+    }
+    if (context.OpenedStrings != context.ClosedStrings) {
+      throw new FormatException("Unterminated string");
+    }
+  }
+
+  private static void EnsureParenthesesAreWellFormed(Token token, ref AnalyzingContext context) {
+    if (token.TokenType == TokenType.OpeningParenthesis) {
+      context.NumberOfOpenedParentheses++;
+    } else if (token.TokenType == TokenType.ClosingParenthesis) {
+      context.NumberOfClosedParentheses++;
+    }
+  }
+
+  private static void EnsureStringsAreWellFormed(Token token, ref AnalyzingContext context) {
+    if (!context.IsInString && token.TokenType == TokenType.String) {
+      context.IsInString = true;
+      context.OpenedStrings++;
+    } else if (context.IsInString && token.TokenType == TokenType.String) {
+      context.IsInString = false;
+      context.ClosedStrings++;
+    }
+  }
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/Token.cs b/EpplusFormulaParser/LexicalAnalysis/Token.cs
new file mode 100644
index 0000000..397cdd5
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/Token.cs
@@ -0,0 +1,50 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public class Token(string token, TokenType tokenType) {
+  public string Value { get; } = token;
+
+  public TokenType TokenType { get; internal set; } = tokenType;
+
+  public bool IsNegated { get; private set; }
+
+  public void Negate() {
+    if (TokenType is TokenType.Decimal or TokenType.Integer or TokenType.ExcelAddress) {
+      IsNegated = true;
+    }
+  }
+
+  public override string ToString() {
+    return TokenType + ", " + Value;
+  }
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/TokenFactory.cs b/EpplusFormulaParser/LexicalAnalysis/TokenFactory.cs
new file mode 100644
index 0000000..9084591
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/TokenFactory.cs
@@ -0,0 +1,115 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ * Jan Källman                      Replaced Adress validate    2013-03-01
+ * *******************************************************************************/
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace EpplusFormulaParser;
+
+internal static partial class TokenFactory {
+  public static Token Create(List<Token> tokens, string token) {
+    if (TokenSeparatorProvider.Tokens.TryGetValue(token, out var tokenSeparator)) {
+      return tokenSeparator;
+    }
+    var tokenList = (IList<Token>)tokens;
+    //Address with worksheet-string before  /JK
+    if (token.StartsWith('!') && tokenList[^1].TokenType == TokenType.String) {
+      var i = tokenList.Count - 2;
+      if (i > 0) {
+        string addr;
+        if (tokenList[i].TokenType == TokenType.StringContent) {
+          addr = "'" + tokenList[i].Value.Replace("'", "''") + "'";
+        } else {
+          throw new ArgumentException($"Invalid formula token sequence near {token}");
+        }
+        //Remove the string tokens and content
+        tokenList.RemoveAt(tokenList.Count - 1);
+        tokenList.RemoveAt(tokenList.Count - 1);
+        tokenList.RemoveAt(tokenList.Count - 1);
+
+        return new(addr + token, TokenType.ExcelAddress);
+      }
+      throw new ArgumentException($"Invalid formula token sequence near {token}");
+    }
+
+    if (tokens.Count != 0 && tokens.Last().TokenType == TokenType.String) {
+      return new(token, TokenType.StringContent);
+    }
+    if (!string.IsNullOrEmpty(token)) {
+      token = token.Trim();
+    }
+    if (DecimalRegex().IsMatch(token)) {
+      return new(token, TokenType.Decimal);
+    }
+    if (IntegerRegex().IsMatch(token)) {
+      return new(token, TokenType.Integer);
+    }
+    if (BooleanRegex().IsMatch(token)) {
+      return new(token, TokenType.Boolean);
+    }
+    if (token.Contains("#REF!", StringComparison.InvariantCultureIgnoreCase)) {
+      return new(token, TokenType.InvalidReference);
+    }
+    if (token.Equals("#NUM!", StringComparison.InvariantCultureIgnoreCase)) {
+      return new(token, TokenType.NumericError);
+    }
+    if (token.Equals("#VALUE!", StringComparison.InvariantCultureIgnoreCase)) {
+      return new(token, TokenType.ValueDataTypeError);
+    }
+    if (token.Equals("#NULL!", StringComparison.InvariantCultureIgnoreCase)) {
+      return new(token, TokenType.Null);
+    }
+    if (FunctionRepository.IsFunctionName(token)) {
+      return new(token, TokenType.Function);
+    }
+    if (tokenList.Count > 0 && tokenList[^1].TokenType == TokenType.OpeningEnumerable) {
+      return new(token, TokenType.Enumerable);
+    }
+    var at = ExcelAddressUtilities.IsValid(token);
+    if (at == ExcelAddressUtilities.AddressType.InternalAddress) {
+      return new(token.ToUpper(CultureInfo.InvariantCulture), TokenType.ExcelAddress);
+    }
+    return new(token, TokenType.Unrecognized);
+  }
+
+  [GeneratedRegex(@"^[0-9]+\.[0-9]+$")]
+  private static partial Regex DecimalRegex();
+
+  [GeneratedRegex("^[0-9]+$")]
+  private static partial Regex IntegerRegex();
+
+  [GeneratedRegex("^(true|false)$", RegexOptions.IgnoreCase)]
+  private static partial Regex BooleanRegex();
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/TokenSeparatorProvider.cs b/EpplusFormulaParser/LexicalAnalysis/TokenSeparatorProvider.cs
new file mode 100644
index 0000000..f505227
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/TokenSeparatorProvider.cs
@@ -0,0 +1,70 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Frozen;
+using System.Collections.Generic;
+
+namespace EpplusFormulaParser;
+
+internal static class TokenSeparatorProvider {
+  private static readonly FrozenDictionary<string, Token> _tokens = new Dictionary<string, Token> {
+    { "+", new("+", TokenType.Operator) },
+    { "-", new("-", TokenType.Operator) },
+    { "*", new("*", TokenType.Operator) },
+    { "/", new("/", TokenType.Operator) },
+    { "^", new("^", TokenType.Operator) },
+    { "&", new("&", TokenType.Operator) },
+    { ">", new(">", TokenType.Operator) },
+    { "<", new("<", TokenType.Operator) },
+    { "=", new("=", TokenType.Operator) },
+    { "<=", new("<=", TokenType.Operator) },
+    { ">=", new(">=", TokenType.Operator) },
+    { "<>", new("<>", TokenType.Operator) },
+    { "(", new("(", TokenType.OpeningParenthesis) },
+    { ")", new(")", TokenType.ClosingParenthesis) },
+    { "{", new("{", TokenType.OpeningEnumerable) },
+    { "}", new("}", TokenType.ClosingEnumerable) },
+    { "'", new("'", TokenType.String) },
+    { "\"", new("\"", TokenType.String) },
+    { ",", new(",", TokenType.Comma) },
+    { ";", new(";", TokenType.SemiColon) },
+    { "[", new("[", TokenType.OpeningBracket) },
+    { "]", new("]", TokenType.ClosingBracket) },
+    { "%", new("%", TokenType.Percent) },
+  }.ToFrozenDictionary();
+
+  public static IDictionary<string, Token> Tokens => _tokens;
+
+  public static bool IsOperator(string item) =>
+    _tokens.TryGetValue(item, out var token) && token.TokenType == TokenType.Operator;
+
+  public static bool IsPossibleLastPartOfMultipleCharOperator(string part) => part is "=" or ">";
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/TokenType.cs b/EpplusFormulaParser/LexicalAnalysis/TokenType.cs
new file mode 100644
index 0000000..0c689c0
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/TokenType.cs
@@ -0,0 +1,60 @@
+﻿/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+namespace EpplusFormulaParser;
+
+public enum TokenType {
+  Operator,
+  Negator,
+  OpeningParenthesis,
+  ClosingParenthesis,
+  OpeningEnumerable,
+  ClosingEnumerable,
+  OpeningBracket,
+  ClosingBracket,
+  Enumerable,
+  Comma,
+  SemiColon,
+  String,
+  StringContent,
+  Integer,
+  Boolean,
+  Decimal,
+  Percent,
+  Function,
+  ExcelAddress,
+  NameValue,
+  InvalidReference,
+  NumericError,
+  ValueDataTypeError,
+  Null,
+  Unrecognized,
+}
diff --git a/EpplusFormulaParser/LexicalAnalysis/TokenizerContext.cs b/EpplusFormulaParser/LexicalAnalysis/TokenizerContext.cs
new file mode 100644
index 0000000..76b839a
--- /dev/null
+++ b/EpplusFormulaParser/LexicalAnalysis/TokenizerContext.cs
@@ -0,0 +1,79 @@
+/*******************************************************************************
+ * You may amend and distribute as you like, but don't remove this header!
+ *
+ * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
+ * See http://www.codeplex.com/EPPlus for details.
+ *
+ * Copyright (C) 2011  Jan Källman
+ *
+ * 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.
+ *
+ * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
+ * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
+ *
+ * All code and executables are provided "as is" with no warranty either express or implied.
+ * The author accepts no liability for any damage or loss of business that this product may cause.
+ *
+ * Code change notes:
+ *
+ * Author							Change						Date
+ * ******************************************************************************
+ * Mats Alm   		                Added       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
+ *******************************************************************************/
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace EpplusFormulaParser;
+
+internal sealed class TokenizerContext(string formula) {
+  private StringBuilder _currentToken = new();
+
+  public string Formula { get; } = formula;
+
+  public List<Token> Result { get; } = [];
+
+  public bool IsInString { get; private set; }
+
+  public void ToggleIsInString() {
+    IsInString = !IsInString;
+  }
+
+  internal int BracketCount { get; set; }
+
+  public string CurrentToken => _currentToken.ToString();
+
+  public bool CurrentTokenHasValue =>
+    !string.IsNullOrEmpty(IsInString ? CurrentToken : CurrentToken.Trim());
+
+  public void NewToken() {
+    _currentToken = new();
+  }
+
+  public void AddToken(Token token) {
+    Result.Add(token);
+  }
+
+  public void AppendToCurrentToken(char c) {
+    _currentToken.Append(c.ToString());
+  }
+
+  public void ReplaceLastToken(Token newToken) {
+    var count = Result.Count;
+    if (count > 0) {
+      Result.RemoveAt(count - 1);
+    }
+    Result.Add(newToken);
+  }
+
+  public Token? LastToken => Result.Count > 0 ? Result.Last() : null;
+}