Hi, Following the example from program_options/overview.html, I tried positional_options_description pd; pd.add("output-file", 2).add_optional("input-file", -1); This doesn't work: positional_options_description::add() returns 'void', and add_optional() is probably a typo for add() ? Currently, the only way to get this to work seems to be positional_options_description pd; pd.add("output-file", 2); pd.add("input-file", -1); But following the style of the rest of the library, I expect it was intended that positional_options_description::add() would return a reference to *this ? Using boost 1.33.1, the CVS version of positional_options.hpp is unchanged. Cheers, Ian McCulloch