Ast RTL: Map, Reduce, Where, Any

Src/Data/Myc.Data.Scalar.pas

@@ -254,6 +254,16 @@ type
         property TotalCount: Int64 read GetTotalCount;
     end;
 
+    TIndexSeries = class(TInterfacedObject, ISeries)
+    private
+        FIndexArray: TArray<Integer>;
+        function GetCount: Int64;
+        function GetTotalCount: Int64;
+        function GetItems(Idx: Integer): TScalar;
+    public
+        constructor Create(const AIndexArray: TArray<Integer>);
+    end;
+
     TBinaryOperatorHelper = record helper for TBinaryOperator
         function ToString: string;
     end;
@@ -1557,6 +1567,34 @@ begin
     Result := FTotalCount;
 end;
 
+{ TIndexSeries }
+
+constructor TIndexSeries.Create(const AIndexArray: TArray<Integer>);
+begin
+    inherited Create;
+    FIndexArray := AIndexArray;
+end;
+
+function TIndexSeries.GetCount: Int64;
+begin
+    Result := Length(FIndexArray);
+end;
+
+function TIndexSeries.GetTotalCount: Int64;
+begin
+    Result := GetCount;
+end;
+
+function TIndexSeries.GetItems(Idx: Integer): TScalar;
+var
+    sourceIndex: Integer;
+begin
+    // The series maintains the "0 is newest" convention.
+    // The index array was built from oldest to newest, so we access it in reverse.
+    sourceIndex := FIndexArray[GetCount - 1 - Idx];
+    Result := TScalar.FromInteger(sourceIndex);
+end;
+
 initialization
     Assert(sizeof(TScalarValue) = 8);