On Saturday, 18 October 2014 at 23:10:15 UTC, Ola Fosheim Grøstad
wrote:
On Saturday, 18 October 2014 at 08:22:25 UTC, monarch_dodra
wrote:
Besides, the code uses x + 1, so the code is already in
undefined state. It's just as wrong as the "horrible code with
UB" we wère trying to avoid in the first place.
So much for convincing me that it's a good idea...
Not sure if you are saying that modulo-arithmetic as a default
is a bad or good idea?
Op usually suggested that all overflows should be undefined
behavior, and that you could "pre-emptivelly" check for overflow
with the above code. The code provided itself overflowed, so was
also undefined.
What I'm pointing out is that working with undefined behavior
overflow is exceptionally difficult, see later.
In D and (C++ for uint) it is modulo-arithmetic so it is
defined as a circular type with at discontinuity which makes
reasoning about integers harder.
What interesting is that overflow is only defined for unsigned
integers. signed integer overflow is *undefined*, and GCC *will*
optimize away any conditions that rely on it.
One thing I am certain of, is that making overflow *undefined* is
*much* worst than simple having modulo arithmetic. In particular,
implementing trivial overflow checks is much easier for the
average developper. And worst case scenario, you can still have
library defined checked integers.
