-
- } else if (other->return_type() == return_types::commutative) {
-
-#if 1
- // This handles eps.i.j.k * p.j * p.k = 0 and related cases.
- // Actually, simplify_indexed() can handle most of them on its own
- // but one specific case that is not covered there is
- // eps~mu.nu~i~j * p.mu * p~nu
- // because of the difference in variance in the dummy indices mu
- // and nu. Eventually, simplify_indexed() should be extended to
- // handle this case, and this hack removed.
- exvector c;
-
- // Handle all indices of the epsilon tensor
- for (int i=0; i<num; i++) {
- ex idx = self->op(i+1);
-
- // Look whether there's a contraction with this index
- exvector::const_iterator ait, aitend = v.end();
- for (ait = v.begin(); ait != aitend; ait++) {
- if (ait == self)
- continue;
- if (is_a<indexed>(*ait) && ait->return_type() == return_types::commutative && ex_to<indexed>(*ait).has_dummy_index_for(idx) && ait->nops() == 2) {
-
- // Yes, did we already have another contraction with the same base expression?
- ex base = ait->op(0);
- if (std::find_if(c.begin(), c.end(), bind2nd(ex_is_equal(), base)) == c.end()) {
-
- // No, add the base expression to the list
- c.push_back(base);
-
- } else {
-
- // Yes, the contraction is zero
- *self = _ex0;
- *other = _ex0;
- return true;
- }
- }
- }
- }
-#endif