if((parse[i - 1].type == "int" ||
                parse[i - 1].type == "float" ||
                parse[i - 1].type == "string" ||
                parse[i - 1].type == "var_int" ||
                parse[i - 1].type == "var_float" ||
                parse[i - 1].type == "var_string" ||
                parse[i - 1].type == "func" ||
                parse[1 - 1].type == "user_func")
                &&
               (parse[i + 1].type == "int" ||
                parse[i + 1].type == "float" ||
                parse[i + 1].type == "string" ||
                parse[i + 1].type == "var_int" ||
                parse[i + 1].type == "var_float" ||
                parse[i + 1].type == "var_string" ||
                parse[i + 1].type == "func" ||
                parse[1 + 1].type == "user_func"))
            { }
            else {
                std::cout << ">>> SYNTAX ERROR: invalid operator placement." << std::endl;
                return false;
            }