On 11/07/2012 04:13 AM, martin wrote:
On Wednesday, 7 November 2012 at 02:58:57 UTC, Era Scarecrow wrote:
Maybe a very simple change/addition; Like perhaps @ref? (Attribute
ref, Alternate ref, auto ref.. All sorta fit for it's meaning).
So...
void func1(ref int x); //D lvalue-only ref
void func2(@ref int x); //works like c++'s ref
Seems fairly easy to tell apart, and still leaves const-ness as an
option.
Afaik C++ doesn't allow rvalues to be passed to _mutable_ references
(T&), only to const references, making perfect sense imo. I really do
not see the point for an additional syntax for C++-like const references
(const T&) which would also take rvalues.
You are still missing that const in C++ is different from const in D.
Also, if the point is to have higher speed, why shouldn't the function
be allowed to use an rvalue as scratch space without a _deep copy_ ?
const in C++ does not mean anything. It is just loosely enforced
interface documentation. const in D actually restricts what the callee
can do with the argument, in a transitive fashion.
Please give me an example where you want to pass an rvalue to a
_mutable_ reference parameter.
When my struct does not support any operations that are const, and
creating a mutable copy is not possible due to indirections?
I would simply continue to disallow that,
since that would mean that changes to the referenced rvalue would not be
visible for the caller (a temporary/literal is changed - how could
someone possibly want that?).
The change may well be visible...
class C{
int x;
}
struct W{
C c;
}
W createW(C c){ return W(c); }
void foo(ref W w){ w.c.x = 2; }
void main(){
C c = new C;
assert(c.x==0);
foo(createW(c));
assert(c.x==2);
}
