Re: [Boost-users] [boost] [program options] Recommended way to specify a list of strings

Subject: Re: [Boost-users] [boost] [program options] Recommended way to specify a list of strings
From: TSalm (tsalm_at_[hidden])
Date: 2010-01-01 11:20:54

>>> How would I specify an empty vector of strings as the default value  
>>> for this
>>> option?
>>>
>>> po::value< vector<string> >()->default_value(??)
>>
>> Use vector<string>() as the default value.
>>
> Hi,
>
> I have the same problem.
> But when I'm using :
>
>    configuration.add_options()
>      ("DEFAULT.bytecompile",program_options::value< vector<string>
>> ()->default_value(vector<string>()))
>      ;
>
> G++ won't compile.
>
> Here is the complete source code :
>
>
> #include <vector>
> #include <boost/program_options.hpp>
>
>
> int main(int argc, char** argv)
> {
>    using namespace std;
>    using namespace boost;
>
>    program_options::options_description configuration;
>    boost::program_options::variables_map vm;
>    vector<string> empty_vector;
>
>    // Set options and default values
>    configuration.add_options()
>      ("DEFAULT.bytecompile",program_options::value< vector<string>
>> ()->default_value(vector<string>()))
>      ;
>
>    program_options::store (
> 	    program_options::parse_command_line(argc, argv, configuration)
> 	  , vm );
>
>    program_options::notify( vm );
>
>    return 0;
> }

Ok. The solution is to specify a "textual" parameter :
      ("DEFAULT.bytecompile",program_options::value< vector<string>  
>()->default_value(vector<string>(),"")

/** Specifies default value, which will be used
     if none is explicitly specified. Unlike the above overload,
     the type 'T' need not provide operator<< for ostream,
     but textual representation of default value must be provided
     by the user.
*/
typed_value* default_value(const T& v, const std::string& textual);