public Parser symbolicChars() {
        if (symbolicCharsParser == null) {
           FutureParser future = scoped("symbolicChars");
           symbolicCharsParser = future;
           future.setParser(
               sequence(
                   token("SYMBOLIC"),
                   optional(
                       choice(
                           token("CHARACTER"),
                           token("CHARACTERS")
                       )
                   ),
                   plus(
                       sequence(
                           plus(
                               literal()
                           ),
                           optional(
                               choice(
                                   token("IS"),
                                   token("ARE")
                               )
                           ),
                           plus(
                               integer()
                           )
                       )
                   ),
                   optional(
                       sequence(
                           token("IN"),
                           identifier()
                       )
                   )
               )
           );
        }

        return symbolicCharsParser;
    }