On Monday, 23 May 2016 at 17:03:32 UTC, Marc Schütz wrote:
On Monday, 23 May 2016 at 15:18:51 UTC, Nick Treleaven wrote:
If we had local refs, we could use this instead:
ref m = matrix.rawArr;
Note that this wouldn't work with rvalues, which `with`
supports.
OK. I suppose supporting local refs is a good reason not to allow
rvalues to be passed as const ref arguments, if the function also
returns by ref.
I think the reason D doesn't support local refs is because it
would make it harder to design @safe, particularly with the
planned @rc ref-counting. Because M() above is only a return
reference, it can't live longer than the data it references.
My ref m could persist longer than matrix.rawArr using (naive)
reference counting.
At some point during the `scope` discussion, Walter wanted to
allow local `ref`s, so I guess he's not opposed to the idea. As
Great :-)
far as I understand, the compiler already supports them
internally, as they can result from lowering certain
constructs, there's just no syntax for them. They wouldn't pose
a problem for lifetime tracking, because they can never be
assigned to, only initialized once.
What about:
@safe unittest
{
RCArray!int arr;
ref r = arr[0];
arr.destroy; // refcount drops to zero, arr.impl memory freed
r++; // writes to unallocated memory
}
