For one, the Index trait is in dire need of an overhaul.
In respect to the operator traits in general, I have actually been thinking of
submitting an RFC proposing that they take thier parameters by-value instead of
by-ref. That would remove the auto-ref behaviour of the operators which is more
consistent with the rest of Rust:
impl<'a, 'b, T> Mul<&'b Mat<T>, Mat<T>> for &'a Mat<T> {
fn mul(&'a self, other: &'b Mat<T>) -> T { ... }
}
let m2: Mat<_> = &m0 * &m1;
~Brendan
On 16 Apr 2014, at 3:23 pm, Artella Coding <[email protected]>
wrote:
> Hi Eric, this is an example of code which gives the error :
>
> ************************************************************
> struct Cls {
> vec : ~[~int]
> }
>
> /*
> Does not compile, yielding error message :
>
> "method `index` has an incompatible type for trait:
> expected concrete lifetime, but found bound lifetime
> parameter &"
> */
> impl<'a> Index<uint,&'a ~int> for Cls {
> fn index(&'a self, i: &uint) -> &'a ~int {
> let val = &'a self.vec[*i];
> return val;
> }
> }
>
> fn main(){}
> ************************************************************
>
> It is easy to write a function which does the exact same thing (for the
> struct above) and has a return type with a bounded lifetime, and therefore it
> does not make sense to me why operator overloading would be restricted in
> this fashion (i.e. restricted to return concrete lifetimes). Thanks.
>
>
>
> On Wed, Apr 16, 2014 at 2:48 AM, Eric Reed <[email protected]> wrote:
> Could you provide a code sample that causes this error?
>
>
> On Tue, Apr 15, 2014 at 6:28 AM, Artella Coding
> <[email protected]> wrote:
>
> Currently if I try to specify lifetimes in the return types of overloaded
> operators like Index ([]), I get an error message :
>
> "method `index` has an incompatible type for trait: expected concrete
> lifetime, but found bound lifetime parameter &"
>
> Why has this restriction been placed, given that I can write custom functions
> which can have bounded lifetimes specifications in the return type?
>
> Thanks
>
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>
>
>
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