* @return the free index (the one that is in iv3 but not in iv2) */
static ex permute_free_index_to_front(const exvector & iv3, const exvector & iv2, int & sig)
{
* @return the free index (the one that is in iv3 but not in iv2) */
static ex permute_free_index_to_front(const exvector & iv3, const exvector & iv2, int & sig)
{