public Parser compilationUnit() {
        if (compilationUnitParser == null) {
           FutureParser future = scoped("compilationUnit");
           compilationUnitParser = future;
           future.setParser(
               sequence(
                   choice(
                       sequence(
                           identificationDivision(),
                           optional(
                               environmentDivision()
                           ),
                           optional(
                               dataDivision()
                           )
                       ),
                       sequence(
                           environmentDivision(),
                           optional(
                               dataDivision()
                           )
                       ),
                       dataDivision()
                   ),
                   optional(
                       sequence(
                           procedureDivision(),
                           star(
                               compilationUnit()
                           )
                       )
                   ),
                   optional(
                       endMarker()
                   )
               )
           );
        }

        return compilationUnitParser;
    }