boost::program_options config file option with multiple tokens

Question

I can not seem to be able to read from config file multitoken options like I can from command line. What is the syntax for the config file?

This is how the option description is added:

//parser.cpp
- - -
po::options_description* generic;
generic=new po::options_description("Generic options");
generic->add_options()
("coordinate",po::value<std::vector<double> >()->multitoken(),"Coordinates (x,y)");

After which I parse command and config-files.

On command line '--coordinate 1 2' works. However, when I try in config file:

coordinate = 1,2

or

coordinate= 1 2

It fails giving a invalid_option_value exception. So what exactly is the syntax for config files in case of multitoken options?

Stanzel

you don't need to use new here. If you do, you risk having memory leaks. – Privatdocent

Answer 1

You can achieve the behavior you seek by writing a custom validator. This custom validator accepts :

./progname --coordinate 1 2
./progname --coordinate "1 2"
#In config file:
coordinate= 1 2

Here is the code:

struct coordinate {
  double x,y;
};

void validate(boost::any& v,
  const vector<string>& values,
  coordinate*, int) {
  coordinate c;
  vector<double> dvalues;
  for(vector<string>::const_iterator it = values.begin();
    it != values.end();
    ++it) {
    stringstream ss(*it);
    copy(istream_iterator<double>(ss), istream_iterator<double>(),
      back_inserter(dvalues));
    if(!ss.eof()) {
      throw po::validation_error("Invalid coordinate specification");
    }
  }
  if(dvalues.size() != 2) {
    throw po::validation_error("Invalid coordinate specification");
  }
  c.x = dvalues[0];
  c.y = dvalues[1];
  v = c;
}
...
    po::options_description config("Configuration");
    config.add_options()
        ("coordinate",po::value<coordinate>()->multitoken(),"Coordinates (x,y)")
        ;

References:

• http://www.boost.org/doc/libs/1_46_1/doc/html/program_options/howto.html#id2219998
• https://stackoverflow.com/tags/boost-program-options/hot
• Handle complex options with Boost's program_options

Vetiver

Answer 2

In your configuration file, put each element of your vector on a different line.

coordinate=1
coordinate=2

Confucius

Answer 3

During finding myself confronted with a similar problem, I took the code above from Rob's answer (from May 4th, 2011), but had to change a few things due to changes in the boost architecture and C++11. I only cite the parts that I changed (or would have changed). The rest that is not within the validate function stays the same. For conformity reasons, I added the necessary std:: prefixes.

namespace po = boost::program_options;

void validate(boost::any& v,
  const std::vector<std::string>& values,
  coordinate*, int) {
  coordinate c;
  std::vector<double> dvalues;
  for(const auto& val : values)  {
    std::stringstream ss(val);
    std::copy(std::istream_iterator<double>(ss), std::istream_iterator<double>(),
      std::back_inserter(dvalues));
    if(!ss.eof()) {
      throw po::invalid_option_value("Invalid coordinate specification");
    }
  }
  if(dvalues.size() != 2) {
    throw po::invalid_option_value("Invalid coordinate specification");
  }
  c.x = dvalues[0];
  c.y = dvalues[1];
  v = c;
}

The shift from po::validation_error to po::invalid_option_value was hinted in https://mcmap.net/q/824828/-how-to-pass-a-string-to-quot-validation_error-quot-method-from-boost-1-46

Nofretete