%start List
%title "A simple comma separated list of integers"
%comment "A trailing comma is allowed."

%%

/* 0 */
List: ListOpt /* Option */;

/* 1 */
ListOpt /* `Option<T>::Some` */
    : Num ListRest ListOpt0 /* Option */;

/* 2 */
ListOpt0 /* `Option<T>::Some` */
    : ",";

/* 3 */
ListOpt0 /* `Option<T>::None` */
    : ;

/* 4 */
ListOpt /* `Option<T>::None` */
    : ;

/* 5 */
ListRest
    : ListRestOpt /* Option */;

/* 6 */
ListRestOpt /* `Option<T>::Some` */
    : "," Num ListRest;

/* 7 */
ListRestOpt /* `Option<T>::None` */
    : ;

/* 8 */
Num : "0|[1-9][0-9]*";