type cell = `Left_Long | `Right_Long | `Left_Short | `Right_Short ;;

type anabaena = [cell]seq ;;

S0 :=  seq:(`Right_Long) ;;

anabaena(S0) ;;

trans grammar = {

  `Right_Short => `Right_Long;

  `Left_Short  => `Left_Long;

  `Right_Long  => `Left_Long, `Right_Short;

  `Left_Long   => `Left_Short, `Right_Long;

} ;;

fun output(S) = (

  foreach c in S do
    switch c
      case `Right_Short: stdout << "r"
      case `Left_Short:  stdout << "l"
      case `Right_Long:  stdout << "R"
      case `Left_Long:   stdout << "L"
    endswitch;
  stdout << "\n";
  S

) ;;

grammar[iter = 5,
        prelude = output,
        interlude = output,
        postlude = output
       ](S0) ;;