Re: [boost] overflow_traits

From: Jason Hise (0xchaos_at_[hidden])
Date: 2006-09-11 09:08:29

I think that adding semantics to the actual operations on integers
(like allowing addition to throw) is dangerous and could easilly cause
unexpected behavior.  Allowing a check to be made before the operation
is performed makes what the code does more clear and explicit, and
doesn't invoke the performance penalty in places where performing the
check is not critical (for instance, if you know at design time that
you are subtracting a positive signed number from another positive
signed number, overflow is impossible).  I suggested some sort of
overflow_traits because I thought it nicely mirrored numeric_traits,
which allows the bounds of a built in type to be determined.

In my case specifically, I only want to test if an operation will
overflow or underflow and do something different as a result.  I am
trying to create a rational number class that does not break under
overflow conditions, but just loses precision instead.  While an
overflow is detected I want to divide both numerator and denominator
by 2 and keep trying.  Also, I plan to support support infinity,
negative infinity, and NaN (1/0, -1/0, and 0/0), so overflows which
are really overflows for the rational type will result in these
values.