Re: [boost] [Boost-users] numeric_cast_traits/cstdint: request forfix in boost1.49

Subject: Re: [boost] [Boost-users] numeric_cast_traits/cstdint: request forfix in boost1.49
From: Brandon Kohn (blkohn_at_[hidden])
Date: 2012-01-28 12:48:10

On 1/28/2012 12:38 PM, Robert Ramey wrote:
> I've taken a careful look at this library as part of something else I'm
> working on.  Its really hard to understand how the library is supposed
> to be used and what facilities it provides.  The usage of policies
> makes it clear that one can customize it, but the default policies
> don't seem to be explained.

I added some documentation for the way to customize policies, but didn't 
get the new docs properly into the 1.48 release branch on time for the 
release. The new docs are in the release trunk. There is an example that 
shows how to override the default policies for a custom numeric type 
using the numeric_cast_traits specialization.

  For example, I had a simple question:
> if I use the library with the default policies to convert an unsigned
> char with a value of 128 to a signed char, what will happen?
> Will an exception be thrown (which is what I want) or will
> something else happen.

I believe the default behavior for the range checker is to see if the 
new type's range as defined in numeric_limits<new type> can represent 
the number. If the number falls out of that range the overflow handler 
will fire. There the default behavior is to throw an overflow exception 
(positive or negative).

>

Brandon