Function new_index_symbols

fem/tensorcoefficient.cpp:153–177

        }

        string new_index_symbols(string existing, size_t nnew) {
            char new_char = 'A';
            auto target_size = existing.size() + nnew;

            while (existing.size() < target_size) {
                if (new_char > 'Z')
                    break;
                if (find(begin(existing), end(existing), new_char) != end(existing))
                    ++new_char;
                else
                    existing += new_char;
            }

            new_char = 'a';
            while (existing.size() < target_size) {
                if (new_char > 'z')
                    throw OutOfIndices("Did not find any unused symbol in A-Z and a-z. Consider using 'optimize_path' and disabling 'einsum_expansion' at some point.");
                if (find(begin(existing), end(existing), new_char) != end(existing))
                    ++new_char;
                else
                    existing += new_char;
            }

            return string{existing.end() - nnew, existing.end()};
        }

        string form_index_signature(const vector<string>& parts)
        {