- if (!indices_consistent(free_indices, free_indices_of_term))
- throw (std::runtime_error("simplify_indexed: inconsistent indices in sum"));
- if (is_ex_of_type(sum, indexed) && is_ex_of_type(term, indexed))
- sum = sum.op(0).bp->add_indexed(sum, term);
- else
- sum += term;
+ if (!term.is_zero()) {
+ if (first) {
+ free_indices = free_indices_of_term;
+ sum = term;
+ first = false;
+ } else {
+ if (!indices_consistent(free_indices, free_indices_of_term))
+ throw (std::runtime_error("simplify_indexed: inconsistent indices in sum"));
+ if (is_ex_of_type(sum, indexed) && is_ex_of_type(term, indexed))
+ sum = sum.op(0).bp->add_indexed(sum, term);
+ else
+ sum += term;
+ }
+ }