Function expand_higher_order_identities

fem/tensorcoefficient.cpp:529–559

        }

        pair<string, Array<shared_ptr<CoefficientFunction>>>
        expand_higher_order_identities(string signature,
                       const Array<shared_ptr<CoefficientFunction>>& cfs,
                       [[maybe_unused]] const map<string, bool> &options) {

          Array<shared_ptr<CoefficientFunction>> new_cfs;
          new_cfs.SetAllocSize(cfs.Size());

          cout << IM(5) << "EinsumCF: expand higher-order identities" << endl;
          auto parts = split_signature(signature);

          for (auto i : Range(cfs))
            if (is_identity(cfs[i]))
            {
              auto dims = cfs[i]->Dimensions();
              stringstream new_part{};
              for (auto j : Range(dims.Size() / 2)) {
                new_cfs.Append(IdentityCF(dims[j]));
                new_part << (j > 0 ? "," : "")
                         << parts[i][j] << parts[i][j + dims.Size() / 2];
              }
              parts[i] = new_part.str();
            }
            else
            {
              new_cfs.Append(cfs[i]);
            }


          return {form_index_signature(parts), std::move(new_cfs)};
        }


        pair<string, Array<shared_ptr<CoefficientFunction>>>