On 05/26/2016 11:13 PM, Era Scarecrow wrote:
By adding a struct overload for opOpAssign I can shrink it all down
to this, and avoid lengths entirely... As such internally the length
starts at 0, and checks are in place to ensure the bounds are never
exceeded.
void scan(ref Data[][] data, Condition cond) {
foreach(i; ...) {
if (cond)
data[i] ~= ...
}
}
Sorry, I'm still lost. Why can't you do whatever you're doing in
opOpAssign directly there, or in a free function? Does the pseudo-array
contain any additional data? Would a wrapper around a built-in array not
work?
[...]
The answer is wrong _because_ the code blows up. I inverted the check
to check if length is at offset 0 since (the length can only be 1 and a
better test), however it _still_ gives the wrong answer. Curiously CTFE
is fine with this casting as long as the pointer stays in that one spot.
Oh, I see. Yeah, the answer is garbage. Seeing the spec section that
Adam D. Ruppe linked, the length field actually comes first.
That CTFE errors out when you move the pointer to a variable screams
that something is wrong. The code seems to be seriously misinterpreted
in CTFE.
----
enum x = () {
size_t[] arr = [13];
return *(cast(size_t*) &arr);
} ();
pragma(msg, x);
----
That prints "13LU". Apparently &arr is mistaken for arr here.
I've filed an issue:
https://issues.dlang.org/show_bug.cgi?id=16081
