boost 如何生成空数组json字符串

Boost库中可以使用json::value构造函数生成空的json数组。例如：

#include <boost/property_tree/json_parser.hpp>
#include <boost/property_tree/ptree.hpp>
#include <iostream>

int main()
{
    boost::property_tree::ptree pt;
    pt.put_child("empty_array", boost::property_tree::ptree{});
    
    std::stringstream ss;
    boost::property_tree::write_json(ss, pt);
    std::string json_string = ss.str();
    
    std::cout << json_string << std::endl; // Output: {"empty_array":[]}
    return 0;
}