Ian McCulloch writes:
Bryan Green wrote:
Vladimir Prus writes:
Speaking about -v -v -v, there's no stock way to achieve that. However,
the provided interfaces seem to make it possible:
1. Derive from value_semantics.
2. Define the 'parse' method to add one to already stored value.
Thanks for the suggestion - I will give it a try!
If it works out, please post the solution to the list. It would be very
useful! Also as an example for how to extend the library.
Done! That wasn't so bad after all. It's pretty cool to see it working.
Hurrah for extensibility!
I created an 'accumulating_value' class, with a 'accum_value()' function.
Here is the usage:
desc.add_options()
("verbose,v", po_ext::accum_value<int>(), "print extra information")
;
...
if (vm.count("verbose")) {
verbose = vm["verbose"].as<int>();
It also supports the 'default_value()' method the way I think it should.
Here is the code:
==========================================================================
namespace po_ext {
template
class accumulating_value : public po::typed_value
{
public:
accumulating_value(T* store_to=0)
: po::typed_value(store_to), origin(0)
{
(void) po::typed_value::zero_tokens();
}
accumulating_value* default_value(const T &v)
{
// setting a default value sets the origin to that value
origin = v;
(void) po::typed_value::default_value(v);
return this;
}
accumulating_value* default_value(const T &v,const std::string&
textual)
{
// setting a default value sets the origin to that value
origin = v;
(void) po::typed_value::default_value(v, textual);
return this;
}
void xparse(boost::any& value_store,
const std::vector& new_tokens)
const
{
// if this is the first occurrence of the option, initialize it
// to the origin.
if (value_store.empty())
value_store = boost::any(origin);
++boost::any_cast(value_store);
}
private:
T origin; // the numeric origin from which to increment upward.
};
template <class T>
accumulating_value<T>*
accum_value(T *v)
{
accumulating_value<T>* r = new accumulating_value<T>(v);
return r;
}
template <class T>
accumulating_value<T>*
accum_value()
{
return accum_value<T>(0);
}
}
==========================================================================
