foof2.cpp

#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>

using namespace rapidjson;

int main() {
    const char* json = "{\"thing\":-1.1030161663305387}";
    Document d;
    d.Parse(json);

    StringBuffer roundtripBuffer;
    Writer<StringBuffer> beforeWriter(roundtripBuffer);
    d.Accept(beforeWriter);

    Value& s = d["thing"];
    double thingVal = -1.1030161663305387;
    s.SetDouble(thingVal);

    StringBuffer nativeSetBuffer;
    Writer<StringBuffer> afterWriter(nativeSetBuffer);
    d.Accept(afterWriter);

    std::cout << json << std::endl;
    std::cout << roundtripBuffer.GetString() << std::endl;
    std::cout << nativeSetBuffer.GetString() << std::endl;
    return 0;
}

ivans@cram:~$ g++ simpledom.cpp && ./a.out
{"thing":-1.1030161663305387}
{"thing":-1.103016166330539}
{"thing":-1.1030161663305387}