On 11/6/12 7:48 AM, H. S. Teoh wrote:
On Tue, Nov 06, 2012 at 05:49:44AM +0100, Tommi wrote:
On Tuesday, 6 November 2012 at 04:31:56 UTC, H. S. Teoh wrote:
The problem is that you can't do this in generic code, because
generic code by definition doesn't know how to copy an arbitrary
type.
I'm not familiar with that definition of generic code. But I do feel
that there's a pretty big problem with a language design if the
language doesn't provide a generic way to make a copy of a variable.
To be fair, e.g. C++ doesn't provide that either.
OK I worded that poorly. All I meant was that currently, there is no
generic way to make a copy of something. It could be construed to be a
bug or a language deficiency, but that's how things are currently.
One *could* introduce a new language construct for making a copy of
something, of course, but that leads to all sorts of issues about
implicit allocation, how to eliminate unnecessary implicit copying,
etc.. It's not a simple problem, in spite of the simplicity of stating
the problem.
Here's where user defined @tributes would help a lot. We'd then define
@owned to mention that a class reference field inside an object must be
duplicated upon copy:
class A { ... }
struct B
{
@owned A payload;
A another;
...
}
That way a generic clone() routine could be written.
Andrei
