Boost logo

Boost :

Subject: Re: [boost] [xint] Design Question
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-06-17 07:10:58

Chad Nelson wrote:
> On 06/16/2010 02:31 PM, vicente.botet wrote:
> >> The problem is: what should the library do if the user asks for an
> >> unsigned *non*-fixed-length integer? [...]
> >
> > What about making the difference between two unsigned integers a
> > signed integer?
> That sounds like a useful behavior, but if the developer using the
> library says it should be an unsigned number, I don't think
> the library should override that.

According to an old C book I have (C: A Reference Manual, 2nd ed, Harbison and Steele), "the result of subtracting one unsigned integer from another is always unsigned and therefore cannot be negative." That may not be definitive, and the C++ standard doesn't dictate the type of the result other than, perhaps, by incorporating the C standard to which I have no access, but it certainly sets expectations that your library ought not violate.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

Boost list run by bdawes at, gregod at, cpdaniel at, john at