Re: [Boost-users] [boost::program_options] optional arguments

From: Chris Weed (chrisweed_at_[hidden])
Date: 2007-06-13 12:10:21

I am at a loss of how to do that.
Hopefully someone else can give you a hand.
Chris

On 6/12/07, Bryan Green <bgreen_at_[hidden]> wrote:
> "Chris Weed" writes:
> > On 6/12/07, Bryan Green <bgreen_at_[hidden]> wrote:
> > > Hello,
> > >
> > > Is there a mechanism in boost::program_options for supporting optional
> > > arguments?  If not, is there a suggested program_options-based alternative?
> > >
> >
> > What exactly do you mean by optional arguments?
> > Do you mean like this?
> > http://www.boost.org/doc/html/program_options/howto.html#id1593176
> >
> > Chris
>
> The quotation in my email goes into exact detail - basically, I'm looking
> for functionality equivalent to GNU getopt_long, which has an
> "optional_argument" specifier.  It is a method for optionally associating a
> value with a particular option.
> For example, if I specify a getopt_long parameter to enable listening on a
> socket:
>
>  {"listen",optional_argument,NULL,'l'}
>
> Then, on the command line,
>  '--listen' means to enable listening, using a default port number.
>  '--listen=5000' means enable listening, using port number 5000.
>
> The only way I see to accomplish this with program_options is to make a
> second option called "listen_port".
>
> I've been playing with 'po::value<uint16_t>()->zero_tokens()', but it does
> not work as I had hoped.  I don't really understand how 'zero_tokens' is
> supposed to work, frankly.  It seems to be useful when the value type is
> 'bool', but I don't understand its use for non-boolean types.
>
> -Bryan
>
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