local sq = syntax (e1=token ("a") e2=token ("b") {Seq (e1, e2)}),
      al = syntax (e=(token ("a") | token ("b")) {Alt (e)}),
      rp = syntax (e=token ("a")* {Rep (e)});

printf ("%s\n", parseString (syntax (sq -eof), "ab").string);
printf ("%s\n", parseString (syntax (al -eof), "a").string);
printf ("%s\n", parseString (syntax (al -eof), "b").string);
printf ("%s\n", parseString (syntax (rp -eof), "aaa").string)