How can I create empty array node using boost property_tree of json parser

I'm trying to create an array node in json, which output is like this:

{
    node: ["12", "13"]
}

but when array is empty, it will output this:

{
    node: ""
}

that's not what I want, I need this:

{
    node: []
}

How can I do that ? And I don't need double quotes("") around numbers. Can anyone help ?

My code is like below:

boost::property_tree::ptree pt;
boost::property_tree::ptree array;
for (vector<int>::const_iterator iter = v.begin();
    iter != v.end();
    ++iter)
{
    boost::property_tree::ptree node;
    node.put("code", *iter);
    array.push_back(std::make_pair("", node));
}
pt.add_child("array", array);

Thanks for your attention.

Solution

PSA Boost 1.75.0 introduced Boost JSON; it can doe this: Live Demo
std::cout << json::object{{"node", json::array{}}};

Boost doesn't have a JSON library. It has a property-tree (think: hierarchical configuration formats) library.

documentation: http://www.boost.org/doc/libs/1_58_0/doc/html/property_tree/parsers.html#property_tree.parsers.json_parser

It specifically states that some things are not well-supported:

arrays in JSON are a hack (you cannot represent the empty array)
all type information is lost (everything needs to be JSON string)

This suits the intended application domains for Boost PropertyTree. If it doesn't suit your problem, use a JSON library.