interesting rosparam behavior...

main.cpp

#include <ros/ros.h>

/**

> rosparam set /some_abs_param 1337
> rosparam set /test/foo 16
> ./test
struct!
has member foo: 1
foo: 16
abs: 1337
**/

int main(int argc, char** argv) {
  ros::init(argc, argv, "test");

  ros::NodeHandle nh("~");

  XmlRpc::XmlRpcValue v;
  nh.getParam("/",v);

  if(v.getType() == XmlRpc::XmlRpcValue::TypeStruct) {
    std::cout << "struct!" << std::endl;

    std::cout << "has member foo: " << v.hasMember("foo") << std::endl;
    std::cout << "foo: " << (int)v["foo"] << std::endl;
  }

  if(nh.getParam("/some_abs_param",v)) {
    std::cout << "abs: " << (int)v << std::endl;
  } else {
    std::cerr << "/some_abs_param not found" << std::endl;
  }

  return 0;
}