C#'s greatest mistakes

[Jonathan M Davis]

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