Ranges/algorithms for aggregation

["Luís]

On Friday, 21 March 2014 at 17:20:38 UTC, Luís Marques wrote:
> I think that's why Justin used sort. The hashGroupBy proposed 
> by bearophile would avoid the sort and the additional memory 
> usage though, so that would be even better.

I was thinking, we don't even need the full power of sort. Is 
there a standard algorithm that makes elements with equal keys be 
in sequence, but that otherwise is less expensive than sort?