Re: [Boost-users] program_options range checking?

From: Fredrik Hedman (hedman_at_[hidden])
Date: 2005-08-24 10:50:00

On Wednesday 24 August 2005 15.15, Vladimir Prus wrote:
> Hi Fredrik,
>
> > Here is what I have now:
> >
> >   /*! Check for values greater than min.
> >    */
> >   template <typename T>
> >   class value_gt {
> >   public:
> >     value_gt(std::string const & msg, T min) : msg_(msg), min_(min) {}
> >     void operator()(T const & v) const {
> >       if (v > min_) return;
>
> .......
>
> >   void doSetProgram(Options & options)
> >   {
> >     options.add_options()
> >     ("help,h", "show this message")
> >     ("density",
> >       pgmopt::value<double>()->notifier(
> >               value_gt<double>("density", 1.0)),
>
> .....
>
> > I don't like repeating the type (see code above) and would rather
> > like to have access to the name of the option in the function
> > that does the check.
> >
> > What would be a better solution?  Adding to the validators idea
> > or?
>
> I'd suggest creating a class template derived from typed_value<T>,
> overriding the 'xparse' method and adding the check there, after calling
> the inherited version. This will bring your example down to:
>
>
>      ("density",
>        pgmopt::value_gt<double>("density", "1.0")
>
Hi Vladimir,

This is almost working now,  need to clean it up and add a couple of ctors to 
the class plus an overloaded helper function  for value that returns 
typed_value pointer.  Thanks!  

What is the recommendation regarding namespaces?  Should I put my own stuff
in boost::program_options, or should it be kept outside?

> It would be nicer to write:
>
>      ("density",
>        pgmopt::value<double>()->validator(_1 < 1.0)
>
> (Using boost.lambda to create validator expression), but it's not supported
> yet. It's something I'd like to add, though.
>
That would be very cool!

Two followup questions.

1) is there a way to make a multitoken option stop? As it is now it just
    seems to munch everything...

   --opt1multi 1 2 3 --opt2multi a b c

   would be nice, but how to do it? 

2)  related to this is the question of how to have options like

    vector1 = 1 33 44
    vector2 = 1.0 2.0 3.0 4.0

   in a file that is parsed by parse_config_file? 

   What about the " = "?  Does it really have to be there?  Could it not be   
relegated to a style or more  general rule?
  
--
Cheers!
F.