Am 11.05.2014 23:43, schrieb sclytrack:
On Sunday, 11 May 2014 at 11:42:37 UTC, ponce wrote:
On Sunday, 11 May 2014 at 08:59:42 UTC, Walter Bright wrote:
D also cannot be performance competitive with C++ if pervasive ARC is
used and memory safety is retained. Rust is attempting to solve this
problem by using 'borrowed' pointers, but this is unproven
technology, see my reply to Manu about it.
I work in a C++ shop and as I see it, resource management is becoming
a solved problem:
- resource owners holds a std::unique_ptr<T> on them. Resource release
is taken care by C++ destructors normally. That means to be
exception-safe, each resource type must better have its class.
- resource users eventually "borrow" the resource by taking a raw
pointer out of the unique pointer. What Rust would do with lifetimes
here is ensure that the resource is still there since move semantics
seems pervasive in this language. In C++ we ensure the resource holder
outlive the users.
- std::shared_ptr is not needed with such constraints. This means no
cycles in the object graph. TBH I have yet to find a dependency scheme
that can't be done that way.
When I use D I can't help but think that releasing resources feels
more manual and error-prone ("oops that resource should have been a
struct not a class" and such traps).
I do not have huge concerns about D GC, but I would be glad to have
more support for owned pointers (ie. Unique!T in Phobos or better). I
have no idea how to make it safe ie. ensure the resource outlive its
users.
I like this owner/unique, borrow thing.
@ is managed (currently reference counted)
~ is owner
& is borrow
fn example3() -> int {
let mut x = ~X {f: 3};
let y = &x.f;
x = ~X {f: 4}; // Error reported here.
*y
}
According to Debian Rust is still too experimental to be packaged.
http://web.mit.edu/rust-lang_v0.8/doc/tutorial-borrowed-ptr.html
servo is written in Rust.
https://github.com/mozilla/servo
There is very little use of "@", it's mostly "&" and "~". Heck I didn't
find any @ while casually browsing the code. It's like they are not
using it at all.
I don't know Rust, it is the first day I look (read documentation) at it.
Have you searched for RC<>() and GC<>() as well?
The @ is gone from Rust and replaced by library types.
--
Paulo
