Saturated Arithmetic (Forked from Swift: overflow raises an error)

[Roberto Waltman <techie@...>]

On 06/12/2014 19:48, Tim Hill wrote:
> It’s less “ints behave like C” than “ints follow the behavior of the 
> underlying hardware”, which these days almost always means 2’s 
> complement with overflow. I’m really not too sure clamping is better 
> than overflow .. at least with overflow when it happens it’s (usually) 
> pretty obvious; clamping has greater potential to go undetected. 

That is called "Saturated Arithmetic" and is common in DSP processors. 
In many situations it is the preferred behavior.
Let's say you are implementing a PID loop to control the speed of an 
electric motor.  Adding a small positive correction value to a large 
positive previous value (that will overflow) will result in:
Saturated Arith will give you still a large positive value (with the 
wrong speed.)
2's overflow will give you a large negative value, reversing the motor 
from (close to) full forward speed to (close to) full reverse.
The first error is much more tolerable than the second.

See:  http://en.wikipedia.org/wiki/Saturation_arithmetic

--
Roberto Waltman