Re: [boost] New Boost.XInt Library, request preliminary review

Subject: Re: [boost] New Boost.XInt Library, request preliminary review
From: Chad Nelson (chad.thecomfychair_at_[hidden])
Date: 2010-03-30 10:23:50

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On 03/30/2010 08:23 AM, Peter Dimov wrote:

>> How does one mix code wanting exceptions with code not wanting them?
> 
> Pretty easy (bad_alloc aside (*)), since the only way to get an
> exception when doing integer operations is to divide by zero (**). So
> code not wanting exceptions needs only not divide by zero - problem
> solved. This of course assumes that the exceptions are not delayed via a
> signaling NaN with the express purpose of making your life difficult by
> turning unary op+/- into a throwing operation.

Which is only a problem if you're doing something that produces a NaN.
In XInt, that's rare, and all such cases are very carefully documented.

> (*) And by the way, out of memory is not overflow. It's possible to run
> out of memory while computing an integer that is smaller than another
> integer that already has been computed. This is not what overflow means.

If that was aimed at XInt, note its purpose: it's intended to allow
calculation with numbers of arbitrary length, up to the memory size of
the system. If the system can't provide enough memory for it at some
point, that *is* an overflow -- the number is too large to represent.

That definition is already used in Boost as well, in the Boost.Math
library: "Overflow Error: Occurs when the result is either infinite, or
too large to represent in the numeric type being returned by the function."
- -- 
Chad Nelson
Oak Circle Software, Inc.
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