Why does D not have generics?

[Bruce Carneal]

On Friday, 15 January 2021 at 18:14:22 UTC, Ola Fosheim Grøstad 
wrote:
> On Friday, 15 January 2021 at 18:11:04 UTC, Bruce Carneal wrote:
>> Type erasure can be tricky, even when it is restricted to 
>> basic value types of the same size.  This shows up when 
>> implementing radix sort where one solution is to map to/from 
>> whole numbers (NaN semantics being ignored).
>
> Yes, I think maybe it can work if one cannot retrieve the key. 
> Then one can store it in a coded fashion that sorts correctly 
> as byte sequences?

You can transform to a canonical relop form wherever you'd like, 
of course, but mapping on entry and unmapping on retrieval or 
exit from a collection library would, as you might imagine, lower 
conversion overhead for the second and subsequent relops, reduce 
bloat, and enable kernel fusion.

All of my use cases for this relop type erasure to date have 
involved fused operations where the overhead of an additional 
store/load out of an intermediate collection would have been very 
difficult to swallow.  But if you're looking at something less 
predictable I'm guessing that type erased collections could be a 
win.

If you decide to pursue it, a report on the good, bad and ugly 
would be appreciated.

Good luck.