The Excel Writer consists of an Ada package, Excel_Out, which produces Excel files - as "physical" files, or as other types of data streams.
The creation of an Excel file is as simple as this small procedure:
with Excel_Out;
procedure Small_demo is
xl : Excel_Out.Excel_Out_File;
begin
xl.Create ("Small.xls");
xl.Put_Line ("Hello world !");
xl.Close;
end;Full description in: excel_writer.txt
Excel Writer is free, open-source and released under the MIT License.