On 4/23/13 2:29 PM, Manu wrote:
On 24 April 2013 03:33, Andrei Alexandrescu
<[email protected] <mailto:[email protected]>>
wrote:
The best setup would be:
1. To take lvalues by reference, write "ref".
2. To take lvalues and rvalues by reference, write "auto ref".
That's not a good setup at all. It still doesn't make sense.
There's nothing 'automatic' about it,
There is - it means ref is inferred.
I've specified ref, it is ref,
there's no other choice.
Well "auto ref" means "I don't care whether this is ref or not".
And it relies on a major breaking change to ref, which restricts the
functionality of ref by default.
This is a confusion. There's no reliance on any change to ref. The
breaking changes are related to adding safety. If safety weren't a
concern, a lot of things would be simple.
Stop talking about r-values, rather, consider safety of passing
temporaries. This problem has nothing to do with r-values, this is
equally unsafe:
void f(ref int x);
int x;
f(x);
It's precisely the same problem, and should be fixed with the same solution.
We should make the code above safe as is.
I would rewrite your list as such:
1. 'un-safely' pass a value (may not be a local), write 'ref'
2. safely pass a value (may be a local), write 'scope ref'
3. if you are concerned with templates do you:
3.a. want unsafe auto-ref, type 'auto ref' (only non-locals would
generate 'ref')
3.b. want safe auto-ref, type 'scope auto ref'
This a terrible, terrible list. I'd be ashamed to have to explain this
with a straight face.
I don't know how to respond to this. To me is it painfully obvious
DIP 36 is poor language design and fails to solve a variety of
issues, such as clarifying lifetime of temporaries, safety, and
returning ref from functions.
Lifetime of temporaries is the most basic of principles. A local lives
the life of the function in which it is defined.
Safety is the whole point, and intrinsic to the proposal; safety by
explicit specification, thus the programmer retains the option.
The missing point here is inflicting more complexity on the user.
Andrei
