On Wednesday, 16 October 2013 at 19:49:25 UTC, monarch_dodra
wrote:
On Wednesday, 16 October 2013 at 17:50:48 UTC, Daniel Davidson
wrote:
How do you propose to make a mutable copy *generically*?
You can't. Let alone generically.
If I give you an "immutable int* p", how do you copy it to
"int* p" ?
On Wednesday, 16 October 2013 at 18:11:48 UTC, Daniel Davidson
wrote:
Thanks. It is cute - but not so helpful. The example stands. I
*need* to call a createRFromT.
Their shapes are the same in this simple example because I
simplified. Make R look like:
struct R {
string[string] ss;
int[] j;
}
and the cute trick falls apart. In words, I have an R and I
want to make a T. The R is const the T will be immutable
because the ctor requires it. But it is technically not
immutable until it is initialized.
The problem is that you are taking a const(R). And you can't
assign a const to an immutable. It has nothing to do with
initialization.
Just to clarify: in the code below: createRFromT(t, r) is *not*
meant to imply it will just try an assignment. Rather, it reads
from t and builds its own data for R. The problem is with
initialization - see Simen Kjaeraas response here:
http://forum.dlang.org/post/[email protected]
struct S {
R r;
this(ref const(T) t) immutable {
createRFromT(t, r);
}
}
void createRFromT(ref const(T) t, ref R r) {
//...
}
