BACK
| back box %prec UP { move(BACK, $1, $2); }
back : BACK text { $$ = atoi((char *) $1); } ;
%right UP DOWN BACK FWD
"back", BACK,
if (dir == FWD || dir == BACK) /* fwd, back */
printf("\\h'%s%du'\\*(%d\n", (dir == BACK) ? "-" : "", a, p);
t->bt_order = BACK;
enum { NOT, BACK, FORWARD } bt_order;
BACK(aft, aft, OPND(s));