[boost] [program_options] comma separated options

Subject: [boost] [program_options] comma separated options
From: Alain Miniussi (Alain.Miniussi_at_[hidden])
Date: 2014-02-10 05:34:26

Hi,

Someone asked me if it was possible to "easily" specify an option that 
would allow to specify a vector of values.
The first options that came in mind was to use "multitoken". But that 
solution had to drawback in that situation:
- ambiguous with  respect to positional parameters
- clumsy when you want to allow options to be specified in files, since 
you have to write:
  option  12
  option 42
  ...
instead of:
  option 12 42 19

So I though about using a custom validator, which implies introducing a 
new type too, if I understand correctly.

Something along the lines of:
=======================
...
template<typename T>
struct option_sequence {
     std::vector<T> values;
};

template<typename T>
void validate(boost::any& v,
               const std::vector<std::string>& values,
               option_sequence<T>* target_type, int)
{
     namespace po  = boost::program_options;
     namespace alg = boost::algorithm;
     std::vector<T> result;
     typedef std::vector<std::string> strings;
     for ( strings::const_iterator iter = values.begin(); iter != 
values.end();
           ++iter ) {
         strings tks;
         alg::split(tks, *iter, alg::is_any_of(":"));
         for( strings::const_iterator tk = tks.begin(); tk != tks.end(); 
++tk) {
             result.push_back(boost::lexical_cast<T>(*tk));
         }
     }
     v = option_sequence<T>();
boost::any_cast<option_sequence<T>&>(v).values.swap(result);
}

int
main(int argc, char* argv[]) {
    ....
     desc.add_options()
         ("values,v", po::value<option_sequence<int> >(), "a vector of 
':' separated values as in \"12:42:-20\".");

===================

Obviously, one could think that some flexibility could be added 
(separators for starters) but you get the idea.

Is that the right way to go (the intermediate option_sequence template 
seems clumsy for the user (but you need to distinguish from 
std::vector's) and if yes, could such a thing be added to the library ? 
(if yes a could propose a patch for consideration).

Cheers

-- 
=====================================
Alain Miniussi
DSI/Pôle Génie Logiciel Scientifique
Observatoire de la Côte d'Azur