On Sun, 14 Feb 2010 17:02:12 -0500, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
dsimcha wrote:
== Quote from Andrei Alexandrescu (seewebsiteforem...@erdani.org)'s
article
ulong x0;
static assert(!__traits(compiles, -x0));
uint x1;
static assert(!__traits(compiles, -x1));
ushort x2;
static assert(!__traits(compiles, -x2));
ubyte x3;
static assert(!__traits(compiles, -x3));
Sounds good?
Andrei
The more you bring up features to give the axe to, the more I find it
funny that,
not being a very good language lawyer, I wasn't aware that half of
these features
existed in the first place. This is one of them. Yes, definitely get
rid of it.
It makes absolutely no sense. If you want to treat your number like a
signed
int, then it should require an explicit cast.
I said the same. Walter's counter-argument is that 2's complement
arithmetic is an inescapable reality that all coders must be aware of in
D and its kin. Negation is really taking the two's complement of the
thing. The fact that the type was unsigned is not of much import.
I'd say 99% of the cases where assigning a negative number to an unsigned
type is the literal -1 (i.e. all bits set). It's just as easy to type ~0.
In fact, in any case that you are using a literal besides that, it's
usually more helpful to type the hex representation, or use ~(n-1) where
you compute n-1 yourself (as in the -1 case).
are there any good cases besides this that Walter has? And even if there
are, we are not talking about silently mis-interpreting it. There is
precedent for making valid C code an error because it is error prone.
If no good cases exist, I'd say drop it.
-Steve
