[boost] Re: numeric_cast

From: Dill, John (john-dill_at_[hidden])
Date: 2004-04-20 14:27:29

"Rob Stewart" <stewart_at_[hidden]> wrote in message news:<200404201905.i3KJ55e08992_at_[hidden]>...
> From: "Dill, John" <john-dill_at_[hidden]>
> > 
> > I am wondering about the use-case of numeric_cast in this sample.
> > 
> > unsigned char uchar_max = std::numeric_limits<unsigned char>::max();
> > char schar_value = 0;
> > 
> > try {
> >   schar_value = boost::numeric_cast<char>( uchar_max );
> > }
> > catch ( boost::bad_numeric_cast )
> > { std::cout << "Overflow occurred..." << std::endl; }
> > 
> > When I execute this sample, I don't get the exception.  What's
> > the background on this behavior?  I'm using gcc 3.3.1.
> 
> Your char is unsigned.

I'd like to know why conceptually the exception isn't thrown.  Why is it beneficial to have unsigned T to signed T overflows not be detected?  It is not just char, but short, int, and long as well.

If this was the intended behavior, then what is the reasoning behind it?

Thanks,
John