Gotcha. But it is still pretty flexible in that you are not bound to the
impls that were originally defined on the type (e.g. like C++/Java where
the list of interfaces implemented by a class are fixed). This relieves one
form writing wrapper classes in order for certain structs to adhere to
particular interfaces.
--
Ziad
On Tue, Nov 5, 2013 at 8:25 PM, Steven Blenkinsop <steven...@gmail.com>wrote:
> Here you own the trait "Double". Doesn't work if you were trying to
> implement a trait you hadn't just defined. The specific examples you
> mentioned were Clone and Drop, so that wouldn't work.
>
>
> On Tuesday, November 5, 2013, Ziad Hatahet wrote:
>
>> The following seems to work:
>>
>> trait Double {
>> fn double(&self) -> Self;
>> }
>>
>> impl Double for int {
>> fn double(&self) -> int {
>> *self * 2
>> }
>> }
>>
>> fn main() {
>> let x = 2;
>> println!("{}", x.double()); // prints "4"
>> }
>>
>>
>>
>> --
>> Ziad
>>
>>
>> On Tue, Nov 5, 2013 at 1:29 PM, Steven Blenkinsop <steven...@gmail.com>wrote:
>>
>>> As long as "you" are the person who owns the type, yeah, but I suspect
>>> that's not what you mean. Coherence requires that you only implement traits
>>> for types if you own either the trait or the type (or both). You can't
>>> implement a 3rd party trait for a 3rd party type, since then there could be
>>> multiple such implementations for a given (trait, type) pair, and coherence
>>> would be broken.
>>>
>>>
>>> On Tue, Nov 5, 2013 at 2:28 PM, Ziad Hatahet <hata...@gmail.com> wrote:
>>>
>>>> On Tue, Nov 5, 2013 at 9:17 AM, Patrick Walton <pcwal...@mozilla.com>wrote:
>>>>
>>>>> On 11/5/13 2:44 AM, spir wrote:
>>>>>
>>>>>> Why not just add a declaration of the trait at the top of the struct
>>>>>> type def?
>>>>>>
>>>>>> struct PairList<Val> : Iterable {
>>>>>>
>>>>>
>>>>> You can implement traits on types that aren't structs.
>>>>
>>>>
>>>>
>>>> Isn't another effect of this is the ability to "monkey-patch" structs
>>>> to implement extra methods or traits? E.g. you can later in implement a
>>>> to_str() method for a type, or implement certain traits, like Clone or
>>>> Drop.
>>>>
>>>>
>>>> --
>>>> Ziad
>>>>
>>>>
>>>> _______________________________________________
>>>> Rust-dev mailing list
>>>> Rust-dev@mozilla.org
>>>> https://mail.mozilla.org/listinfo/rust-dev
>>>>
>>>>
>>>
>>
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