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.
