[boost] Re: Re: [program_options] post-review version

19 Mar 2004

      Vladimir Prus wrote:
...
Neal D. Becker wrote:
...
Why not a default validator?
namespace po = boost::program_options;
namespace boost { namespace program_options {
  template<typename T>
  void validator<T>::operator()(any& v, const vector<string>& xs)
  {
  }
}}
This solves my immediate problem, which is that (strangely)
program_options has a validator for float but not for double.
I think it is addressed. You would just use
value<double>()
and it should work. The previous version had explicit instantiation for
some types, but it no longer the case.
Doesn't work for me:

Here is test program:
#include <boost/program_options.hpp>
#include <iostream>

using namespace std;
namespace po = boost::program_options;

// namespace boost { namespace program_options {
//   template<typename T>
//   void validator<T>::operator()(any& v, const vector<string>& xs)
//   {
//     validators::check_first_occurence(v);
//     string s(validators::get_single_string(xs));
//     try {
//       v = any(lexical_cast<T>(s));
//     }
//     catch(const bad_lexical_cast&) {
//       throw validation_error("'" + s + "' doesn't look like right");
//     }
//   }
// }}

int main (int argc, char** argv) {
  try {

    po::options_description desc("Allowed options");
    desc.add_options()
      ("help", "produce help message")
      ("compression", po::value<int>(), "set compression level")
      ("stupidity", po::value<double>(), "set stupidity level")
      ;

    po::variables_map vm;

    po::store(po::parse_command_line(argc, argv, desc), vm);
    po::notify(vm);

    if (vm.count("help")) {
      cout << desc << "\n";
      return 1;
    }

    if (vm.count("compression")) {
      cout << "Compression level was set to " 
           << vm["compression"].as<int>() << ".\n";
    } else {
      cout << "Compression level was not set.\n";
    }
    if (vm.count("stupidity")) {
      cout << "Stupidity level was set to " 
           << vm["stupidity"].as<double>() << ".\n";
    } else {
      cout << "Stupidity level was not set.\n";
    }
  }
  catch (exception& e) {
    cerr << "error: " << e.what() << '\n';
  }

}
Result:

make 
g++ -g -I /usr/local/src/boost_1_31_0 -o Test1 Test1.cc
-L /usr/local/src/boost_1_31_0/stage/lib -l boost_program_options-gcc
/tmp/cceRudK0.o(.gnu.linkonce.t._ZNK5boost15program_options11typed_valueIdE5parseERNS_3anyERKSt6vectorISsSaISsEE+0x14):
In function
`boost::program_options::typed_value<double>::parse(boost::any&,
std::vector<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >, std::allocator<std::basic_string<char,
std::char_traits<char>, std::allocator<char> > > > const&) const':
/usr/local/src/boost_1_31_0/boost/detail/shared_count.hpp:145: undefined
reference to `boost::program_options::validator<double>::operator(
(boost::any&, std::vector<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >, std::allocator<std::basic_string<char,
std::char_traits<char>, std::allocator<char> > > > const&)'
collect2: ld returned 1 exit status
make: *** [Test1] Error 1

Uncomment the validator and it works.