shift2
| box sub box sbox %prec SUB { shift2($1, $3, $4); }
shift2(p, p1, p2);
printf("%d[%d,%d]: ", n->id, n->shift1, n->shift2);
c->root->shift2 = c->mindepth;
l->node->shift2 = c->root->shift2;
r->shift2 = c->mindepth;
if (r->out && (k < state->shift2)) {
state->shift2 = k;
if (n->shift2 < nn->shift2)
nn->shift2 = n->shift2;
if (k > ostate->shift2)
k = ostate->shift2;
short shift2;