KennyTM~ wrote:
On Jun 17, 10 21:04, Don wrote:
KennyTM~ wrote:
On Jun 17, 10 18:59, Don wrote:
Kagamin wrote:
Don Wrote:
(D has introduced ANOTHER instance of this with the ridiculous >>>
operator.
byte b = -1;
byte c = b >>> 1;
Guess what c is!
)
:)
Well, there was issue. Wasn't it fixed?
No. It's a design flaw, not a bug. I think it could only be fixed by
disallowing that code, or creating a special rule to make that code do
what you expect. A better solution would be to drop >>>.
I disagree. The flaw is whether x should be promoted to
CommonType!(typeof(x), int), given that the range of typeof(x >>> y)
should never exceed the range of typeof(x), no matter what value y is.
The range of typeof(x & y) can never exceed the range of typeof(x), no
matter what value y is. Yet (byte & int) is promoted to int.
That's arguable. But (byte & int -> int) is meaningful because (&) is
some what "symmetric" compared to (>>>).
See below. It's what C does that matters.
Actually, what happens to x>>>y if y is negative?
x.d(6): Error: shift by -1 is outside the range 0..32
If y is a variable, it actually performs x >>> (y&31);
So it actually makes no sense for it to cast everything to int.
The current rule is:
x OP y means
cast(CommonType!(x,y))x OP cast(CommonType!(x,y))y
for any binary operation OP.
How can we fix >>> without adding an extra rule?
There's already an extra rule for >>>.
ubyte a = 1;
writeln(typeof(a >>> a).stringof);
// prints "int".
Similarly, (^^), (==), etc do not obey this "rule".
The logical operators aren't relevant. They all return bool.
^^ obeys the rule: typeof(a^^b) is typeof(a*b), in all cases.
IMO, for ShiftExpression ((>>), (<<), (>>>)) the return type should be
typeof(lhs).
I agree that would be better, but it would be a silent change from the C
behaviour. So it's not possible.
