On 3/20/07, Vladimir Prus <ghost@cs.msu.su> wrote:
Tom Bachmann wrote:
<snip>
1 change the values of options in a variables_map
The only way to do this (as far as I can see) is the private interface that the store function uses. I currently do
const_cast<boost::program_options::variable_value&> (vm[opt -> long_name ()]).value () = val;
which is neither clean nor complete (the internal reference to value_semantic is not updated, but this should not be necessary anyway, I think). The easiest fix would be to add a public interface to change the value of an option in a variables map, by making op[] return a non-const reference. I'm not sure if code should be added to call semantic -> notify automically.
Yep, I guess we need non-const-returning[] for sure. We probably should have variable_value overload operator=, and call semantic->notify. Do you think disallowing assignements that change value type is OK? Say, if you try to assign int to value of type double, you get exception.
Add me to the list of people trying to make boost::program_options do a little more than it was originally designed for ;) Just been over this exact problem today. Disallowing assignments that change the value type sounds good to me. You'll probably catch it the way things currently are because variables_map["option"].as<double>() will throw boost::bad_any_cast later on when you try to acess the option again, but an exception on wrongful assignment would be preferable. Regards, -- Tarjei