C#'s greatest mistakes

[BLS]

On 28/11/2010 00:19, Jonathan M Davis wrote:
> On Saturday 27 November 2010 14:59:09 BLS wrote:
>> On 27/11/2010 16:59, Torarin wrote:
>>> 2010/11/27 Andrei Alexandrescu<SeeWebsiteForEmail at erdani.org>:
>>>> We use template constraints for that kind of stuff.
>>>>
>>>> Andrei
>>>
>>> Yes, and that's great, but is there a way to check whether a template
>>> argument matches a defined interface?
>>
>> I could not resist..
>> We should have Implements!
>>
>> Luca has done some work on it.. but it does not compile anymore. However
>> I think the intension is clear.
>> http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&a
>> rticle_id=101673
>
> If you're checking whether it implements an interface, then : should work just
> like it does with classes. If you're checking whether it has the same functions
> that an interface requires, then you're not really using interfaces correctly.
> structs don't implement interfaces. Classes do that. So, either make it a class,
> or don't use interfaces. If you want to verify that a struct has particular
> functions needed for the template function in question, then just check whether
> calling them compiles ( e.g. __traits(compiles, foo.bar()) ). If you have a set
> of functions that are expected to be there (for instance, to verify that the
> given type is a certain type of range), then just create template which checks
> for each of the functions that are supposed to be there and use the template (
> e.g. isForwardRange!T ). Interfaces and structs don't have anything to do with
> each other.
>
> - Jonathan M Davis

Thanks for taking the time to explain. I've copypasted.
However,
Given that dCollections enable me to change the underlaying algorithm 
(say I can replace the default RBTree with SkipList) In order to so that 
I have to fulfil some requirements. And now, I guess that is what I am 
talking about. I want a guarantee that my skiplist implementation 
fulfills the cursor (a structure) requirements.

So now what is wrong with the contract from dCollections I am asking 
for. Please note that dCollections implements cursors as well as ranges.

Bjoern