multiple-item traversal ranges

[dsimcha]

On 3/30/2011 9:46 PM, Andrei Alexandrescu wrote:
>> Agreed. Andrei's opinion is understandable if he thinks he'd have to
>> implement these features and has better things to do. I'd be willing to
>> do the implementation work if the relevant compiler bugs/enhancements
>> (2443, 4707, and maybe support for inlining delegates) get fixed so I
>> can do it right.
>
> I'm much more worried about the long-term costs associated with such an
> approach.
>

Please elaborate.  My possibly naive opinion is that objects with a 
single-argument opApply are a structural supertype of input ranges 
(since they both support foreach with a single argument), so except for 
a few minor details with regard to the compiler this is a no-brainer. 
It's not a high priority, but it's worth doing for the sake of 
consistency and generality.