Re: [boost] [constrained_value] New version

Subject: Re: [boost] [constrained_value] New version
From: Neal Becker (ndbecker2_at_[hidden])
Date: 2008-11-18 11:54:30

Robert Kawulak wrote:

> Hi all,
> 
> I've updated the Boost Constrained Value library (which is likely to be
> reviewed soon) -- the list of changes is below:
> - added unconstrained -- a new constrained alias to replace it in release
> mode if constraint-checking is not needed and efficiency is a concern,
> - added Examples section to the documentation,
> - other minor corrections and improvements in the documentation,
> - using BOOST_THROW_EXCEPTION instead of boost::throw_exception()
> (requires Boost version 1.37.0),
> - fixed one place to make a better use of EBO.
> 
> As usually, the code and documentation can be downloaded here:
> http://rk.go.pl/f/constrained_value.zip
> The documentation is also available online here:
> http://rk.go.pl/r/constrained_value
> 
Thanks.

I thought to use 'unconstrained', but this isn't really what I need.  I have a fixed_pt integer class, 

//! signed fixed pt
template<int int_bits, int frac_bits, typename base_type=int, typename error_policy=cv::throw_exception<>, typename round_policy=rnd<base_type> >
struct fixed_pt  :
...
  typedef typename cv::bounded_int<base_type, min, max,error_policy>::type val_t;

When I want to turn off checking, it seems the thing to do is use an error_policy which ignores the error.  I've been using this, which I got from you some time ago:

    struct no_error_policy { 
      template <typename V, class C> 
      void operator () (V & old_val, const V & new_val, C &) 
      { 
        old_val = new_val; 
      } 
    };

 
So I can write:
  fixed_pt<16,5,int,cv::no_error_policy> f;

Maybe this is a useful addition to the lib, or at least as an example?