Feature/groupby

src/EPPlus/FormulaParsing/DependencyChain/RpnFormula.cs

@@ -130,6 +130,7 @@ internal LambdaExpressionStackPosition GetCurrentLambdaExpressionStackPosition()
         internal int GetNumberOfLambdaVariables()
         {
             if (_lambdaSettings == null || _lambdaSettings.NumberOfLambdaVariables == null || _lambdaSettings.NumberOfLambdaVariables.Count == 0) return 0;
+            if (_lambdaSettings.CurrentLambdaExpressions.Peek().Expression.ArgumentCollectionStarted == false) return 0;
             return _lambdaSettings.NumberOfLambdaVariables.Peek();
         }
 

src/EPPlus/FormulaParsing/DependencyChain/RpnFormulaExecution.cs

@@ -1130,7 +1130,11 @@ private static FormulaRangeAddress[] ExecuteNextToken(RpnOptimizedDependencyChai
                             {
                                 exp.Status |= ExpressionStatus.IsLambdaVariableDeclaration;
                             }
-
+                            if (t.TokenType == TokenType.EtaReducedLambda)
+                            {
+                                ((FunctionExpression)f._expressions[f._tokenIndex]).SetRpnFormula(f);
+                            }
+
                             var cr = exp.Compile();
                             if (cr.DataType == DataType.LambdaTokens)
                             {
@@ -1140,7 +1144,11 @@ private static FormulaRangeAddress[] ExecuteNextToken(RpnOptimizedDependencyChai
                             {
                                 s.Push(f._expressions[f._tokenIndex]);
                             }
-                            else if (cr.DataType != DataType.LambdaVariableDeclaration && f.LambdaSettings.LambdaArgsAdded.Count > 0 && f.LambdaSettings.LambdaArgsAdded.Peek() < f.GetNumberOfLambdaVariables())
+                            else if(
+                                f._expressionStack.Peek() is LambdaCalculationExpression lce2 && lce2.ArgumentCollectionStarted &&
+                                cr.DataType != DataType.LambdaVariableDeclaration 
+                                && f.LambdaSettings.LambdaArgsAdded.Count > 0 
+                                && f.LambdaSettings.LambdaArgsAdded.Peek() < f.GetNumberOfLambdaVariables())
                             {
                                 leStackPos.Expression.SetVariable(f.LambdaSettings.LambdaArgsAdded.Peek(), cr.Result, cr.DataType, cr.Address);
                                 var nLambdaArgsAdded = f.LambdaSettings.LambdaArgsAdded.Pop();
@@ -1155,10 +1163,7 @@ private static FormulaRangeAddress[] ExecuteNextToken(RpnOptimizedDependencyChai
                         {
                             s.Push(f._expressions[f._tokenIndex]);
                         }
-                        if(t.TokenType == TokenType.EtaReducedLambda)
-                        {
-                            ((FunctionExpression)f._expressions[f._tokenIndex]).SetRpnFormula(f);
-                        }
+
                         break;
                     case TokenType.Negator:
                         s.Push(s.Pop().Negate());
@@ -1735,6 +1740,10 @@ private static IList<CompileResult> CompileFunctionArguments(RpnFormula f, Funct
                     {
                         si.Status |= ExpressionStatus.FunctionArgument;
                     }
+                    if(si is FunctionExpression fe1)
+                    {
+                        fe1.SetRpnFormula(f);
+                    }
                     var cr = si.Compile();
                     list.Insert(0, cr);
                 }

src/EPPlus/FormulaParsing/Excel/Functions/BuiltInFunctions.cs

@@ -336,6 +336,7 @@ public BuiltInFunctions()
             // Reference and lookup
             Functions["address"] = new Address();
             Functions["areas"] = new Areas();
+            Functions["groupby"] = new GroupBy();
             Functions["hlookup"] = new HLookup();
             Functions["vlookup"] = new VLookup();
             Functions["xlookup"] = new Xlookup();

src/EPPlus/FormulaParsing/Excel/Functions/ExcelFunction.cs

@@ -128,6 +128,14 @@
         {
 
         }
+
+        public virtual string Name
+        { 
+            get 
+            {
+                return GetType().Name.ToUpper();
+            }
+        }
         /// <summary>
         /// Indicates that the function is an ErrorHandlingFunction.
         /// </summary>
@@ -895,10 +903,21 @@
 				return true;
 			}
 		}
-		/// <summary>
-		/// Provides information about the functions parameters.
-		/// </summary>
-		public virtual ExcelFunctionParametersInfo ParametersInfo
+        /// <summary>
+        /// The function is allowed...
+        /// </summary>
+        public virtual bool IsAllowedAsLambdaWithMultipleArguments
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Provides information about the functions parameters.
+        /// </summary>
+        public virtual ExcelFunctionParametersInfo ParametersInfo
         {
             get;
         } = ExcelFunctionParametersInfo.Default;

src/EPPlus/FormulaParsing/Excel/Functions/MathFunctions/PercentOf.cs

@@ -26,7 +26,7 @@ internal class PercentOf : ExcelFunction
     {       
         public override int ArgumentMinLength => 2;
         public override string NamespacePrefix => "_xlfn.";
-
+        public override bool IsAllowedAsLambdaWithMultipleArguments => true;
         public override CompileResult Execute(IList<FunctionArgument> arguments, ParsingContext context)
         {
             if (arguments.Count > 2)

src/EPPlus/FormulaParsing/Excel/Functions/MathFunctions/Sum.cs

@@ -24,6 +24,7 @@ namespace OfficeOpenXml.FormulaParsing.Excel.Functions.MathFunctions
     internal class SumV2 : ExcelFunction
     {
         public override int ArgumentMinLength => 1;
+        public override string Name => "SUM";
 
         public override CompileResult Execute(IList<FunctionArgument> arguments, ParsingContext context)
         {