Hi,
The thing is, I want to use function ptr_eq<T>(@T, @T) from
core::managed and I can't change it in the way you describe.
Actually, I'd like to make sure that I can't add twice the same object
to a vector like below :
use core::vec::position;
use core::managed::ptr_eq;
struct DummyListener;
trait Listener { fn fire_event(&self); }
impl Listener for DummyListener { fn fire_event(&self) { /* stuff */ } }
fn main() {
let mut vec: ~[@Listener] = ~[];
let a = @DummyListener;
let b = @DummyListener;
vec = add(vec, a as @Listener);
vec = add(vec, b as @Listener);
vec = add(vec, b as @Listener);
for vec.each |listener| {listener.fire_event();}
}
fn add(mut vec: ~[@Listener], toAdd: @Listener) -> ~[@Listener] {
if ( position(vec, |listener| { ptr_eq::<Listener>(toAdd,
*listener) }) == None) {
vec.push(toAdd);
}
vec
}
What do you mean by you can't cast to Traits, isn't it what 'as' is for ?
On 21/05/2013 14:54, Fedor Indutny wrote:
Hi!
You can't cast structs to traits, traits is just a behaviour for
structs. What you probably wanted to do was:
fn foo<T: ToStr>(value: @T) -> ~str { value.to_str() }
Cheers,
Fedor.
On Tue, May 21, 2013 at 3:50 PM, Vincent O. <[email protected]
<mailto:[email protected]>> wrote:
Hi,
I tried to use core::managed::ptr_eq for boxed traits but it
compile-fails with a mismatched type error.
Here's a code example that reproduces my problem :
use core::ToStr;
fn main() {
let a = @S;
foo::<ToStr>(a as @ToStr);
}
struct S;
impl S for ToStr { fn to-str(&self) -> ~str {~""} }
fn foo<T>(value: @T) {} // similar to ptr_eq
with the error message :
test.rs:5:15: 5:26 error: mismatched types: expected
`@core::to_str::ToStr` but found `@core::to_str::ToStr` (expected
@-ptr but found trait core::to_str::ToStr)
test.rs:5 <http://test.rs:5> test::<ToStr>(a as @ToStr);
The issue is the same with owned boxes. Is it the intended
behavior ? in this case, is there any workaround ?
_______________________________________________
Rust-dev mailing list
[email protected] <mailto:[email protected]>
https://mail.mozilla.org/listinfo/rust-dev
_______________________________________________
Rust-dev mailing list
[email protected]
https://mail.mozilla.org/listinfo/rust-dev
