Function make_join

extensions/expression-language/Expression.cpp:1368–1399

}

Expression make_join(const std::string &function_name, const std::vector<Expression> &args) {
  if (args.size() != 2) {
    std::stringstream message_ss;
    message_ss << "Expression language function " << function_name << " called with " << args.size() << " argument(s), but " << 2 << " are required";
    throw std::runtime_error(message_ss.str());
  }

  if (!args[0].is_multi()) {
    std::stringstream message_ss;
    message_ss << "Expression language function " << function_name << " called against singular expression.";
    throw std::runtime_error(message_ss.str());
  }

  auto delim_expr = args[1];

  return args[0].make_aggregate([delim_expr](const Parameters &params,
      const std::vector<Expression> &sub_exprs) -> Value {
    std::string delim = delim_expr(params).asString();
    std::stringstream out_ss;
    bool first = true;

    for (const auto &sub_expr : sub_exprs) {
      if (!first) {
        out_ss << delim;
      }
      out_ss << sub_expr(params).asString();
      first = false;
    }

    return Value(out_ss.str());
  });
}

Expression make_dynamic_function(const std::string &function_name, const std::vector<Expression> &args) {
  if (function_name == "hostname") {