Re: [Boost-users] program_options: wild write

From: Peter Whaite (boost_at_[hidden])
Date: 2005-11-22 15:08:34

Vladimir Prus <ghost_at_[hidden]> wrote:

> Merrill Cornish wrote:
> 
> > graph_file is a positional parameter.  So should it be added to the
> > option_description list?
> 
> Yes, how else would you specify the type of the value?
> positional_options_description only specifies translation from
> position on the command line to option name, the option still has to
> be registered.  I've added a warning to the docs.

I'm sure a warning will help as that's not at all obvious in the current
documentation.  A comment in the example would be useful too.  It took
me a while for the penny to drop the first time I used this library.

FWIW my (now obviously erroneous) reasoning was that a
positional_options_description was just another kind of
options_description, and that "input-file" was in both of them in
example/program_options.cpp so it could be used as both an option and a
positional argument.  I only wanted it as a positional parameter, so I
omitted it from the options_description.

I also found myself wanting to generate a usage message like this...

  po::positional_options_description pd;
  cout << "Usage: " << progname << " [options]" << pd <<  endl;

rather than having to loop through pd.

But these are minor things. Thank you for a very useful library.
  
---
Peter Whaite.