Re: [Boost-users] program_options: documentation dead end

From: Vladimir Prus (ghost_at_[hidden])
Date: 2007-07-19 02:49:10

Steven Mackenzie wrote:

> Ian McCulloch wrote:
>> Bryan Green wrote:
>> [snip]
>>> While I'm on the subject, you sometimes see something like the
>>> following:
>>>
>>> ./prog -vvv
>>>   or
>>> ./prog -v -v -v
>>>
>>> This would *increment* the verbosity level three times.  I can't see how
>>> to replicate this in program_options.
>> 
>> This is something I have asked about before on this list, but at the time
>> there was no response.  I would be very interested in knowing how to do
>> this using boost::program_options!
> 
> One complete solution has already been posted, but just for diversity,
> setting a notifier function on the variable involves less typing.
> Something like
> 
> int verbosityLevel;
> ...
> verbosityLevel = 0;
> ...
> void VerbosityWatcher( bool val )
> {
> ++verbosityLevel;
> }
> ...
> desc.add_options()
>     ("verbose,v",
> po::bool_switch()
> ->notifier( &VerbosityWatcher ),
> "print extra information")
>     ;

Does this actually work? I think the plan is for notifier
functions to be called only when you call 'notify' on
variables_map. So, notifier will be called only once.

Of course, I might have forgotten how the library actually
works, or there might be a bug.

- Volodya