listing parameters or using a dictionary

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In C++, is there a way to list parameters on the parameter server, optionally those in a particular namespace? Alternatively, can I use a dictionary/map?

I want to put a mapping name/number in a yaml file loaded by roslaunch, and my node should be able to list the names and retrieve the associated number. rosparam list can do that, and associated with grep I can retrieve only the parameters I want. can I do that in C++ directly. the parameter server c++ API does not seem to provide that, or is it hidden? Can it be added in future releases?

I tried using a dictionary but it was expended in a list of parameters instead of being a dictionary data structure, i.e. those 2 yaml files yielded the same result

channel_numbers: {applanix: 0, radar: 1, trimble: 5, velodyne: 10}

and

channel_numbers:
  applanix: 0
  radar: 1
  trimble: 5
  velodyne: 10

I would like something like:

ros::NodeHandle nh("~");
vector<string> parameters = nh.list_parameters("channel_numbers");
// and then for each parameter in parameters get its value...