boost::program_options overloaded validate is ambiguous - boost

Question

I am trying to parse a list input from the command line.
My class is derived from vector
The compiler complains about a overloaded validate being ambiguous.
I can see why, but do not know how to solve this issue.
Please help.
Below is a minimal example that generates the error. If the type of ch_list is changed to a vector, this minimal example compiles.
// g++ -std=c++11 -Wall -Wextra -pedantic test.cpp -o test -lboost_program_options -lboost_system
#include <vector>
#include <boost/program_options.hpp>
#include <iostream>
#include <vector>
using namespace std;
class mylist : public vector<int> {
public:
friend istream &operator>>(istream &is, mylist& l) {
int val;
is >> val;
l.push_back(val);
return is;
}
friend ostream& operator<<(ostream& os, const mylist& l) {
return os << l[0];
}
};
int main (int argc, char* argv[])
{
//vector<int> ch_list; // This works
mylist ch_list; // This doesn't
namespace po = boost::program_options;
po::options_description desc("Allowed options");
desc.add_options()
("ch", po::value<decltype(ch_list)>(&ch_list), "Set channel numbers")
;
po::variables_map vm;
try {
po::store(po::parse_command_line(argc, argv, desc), vm);
po::notify(vm);
}
catch (po::error& e) {
cerr << "ERROR: " << e.what() << "\n";
return EXIT_FAILURE;
}
if (!ch_list.empty())
cout << ch_list[0] << "\n";
return EXIT_SUCCESS;
}
I get these errors
/usr/include/boost/program_options/detail/value_semantic.hpp: In instantiation of ‘void boost::program_options::typed_value<T, charT>::xparse(boost::any&, const std::vector<std::basic_string<charT> >&) const [with T = mylist; charT = char]’:
test.cpp:47:5: required from here
/usr/include/boost/program_options/detail/value_semantic.hpp:169:13: error: call of overloaded ‘validate(boost::any&, const std::vector<std::basic_string<char> >&, mylist*, int)’ is ambiguous
/usr/include/boost/program_options/detail/value_semantic.hpp:169:13: note: candidates are:
/usr/include/boost/program_options/detail/value_semantic.hpp:81:10: note: void boost::program_options::validate(boost::any&, const std::vector<std::basic_string<charT> >&, T*, long int) [with T = mylist; charT = char]
/usr/include/boost/program_options/detail/value_semantic.hpp:129:10: note: void boost::program_options::validate(boost::any&, const std::vector<std::basic_string<charT> >&, std::vector<_RealType>*, int) [with T = int; charT = char]

Answer 1

You can use custom validator. Your code would be:
#include <vector>
#include <boost/program_options.hpp>
#include <iostream>
#include <vector>
using namespace std;
namespace po = boost::program_options;
class mylist : public vector<int> {
public:
};
void validate(boost::any& v,
const vector<string>& values,
mylist*, int) {
mylist dvalues;
for(vector<string>::const_iterator it = values.begin();
it != values.end();
++it) {
stringstream ss(*it);
copy(istream_iterator<int>(ss), istream_iterator<int>(),
back_inserter(dvalues));
if(!ss.eof()) {
throw ("Invalid coordinate specification");
}
}
v = mylist(dvalues);
}
int main (int argc, char* argv[])
{
//vector<int> ch_list; // This works
mylist ch_list; // This doesn't
po::options_description desc("Allowed options");
desc.add_options()
("ch", po::value< mylist >(&ch_list)->multitoken(), "Set channel numbers")
;
po::variables_map vm;
try {
po::store(po::parse_command_line(argc, argv, desc), vm);
po::notify(vm);
}
catch (po::error& e) {
cerr << "ERROR: " << e.what() << "\n";
return EXIT_FAILURE;
}
for (auto cc : ch_list)
cout << cc << endl;
return EXIT_SUCCESS;
}
Reference: boost::program_options config file option with multiple tokens