value range propagation for _bitwise_ OR

[Adam D. Ruppe]

On Sat, Apr 10, 2010 at 02:55:36PM -0400, bearophile wrote:
> Time ago I have even suggested to disallow bitwise ops when one or both operands are signed...

I understand the position, but I don't advocate it just because I think it would
be annoying and not give much of a benefit.

Consider the following:

for(int a = -10; a < 10; a++)
	writeln(a&1 ? "odd" : "even");

I'd just be annoyed if I had to cast a to uint just to do that. Note that it works
on negative numbers too, so it isn't strictly wrong to do it on signed ints.

I use this when doing stripes on outputted tables and stuff like that.

a % 2 does the same thing, so this specific case isn't a big deal, but I still
tend to type &1 rather than %2 out of habit (this kind of thing used to make a
real speed difference back in the DOS days when I learned it all!)

-- 
Adam D. Ruppe
http://arsdnet.net