All right, then: This one is complete (compiles, runs, iterates through the data, accessing only fields "x" and "y"):

  #include <fstream>
  #include <json.hpp>
  
  int main()
  {
  	std::ifstream input_file("data.json");
  	nlohmann::json data;
  	data << input_file;
  	for (auto obj : data)
  		std::cout << obj["x"] << ',' << obj["y"] << '\n';
  }