Ranges/algorithms for aggregation

["Luís]

On Friday, 21 March 2014 at 16:53:46 UTC, H. S. Teoh wrote:
> Be aware, though, that groupBy only compares *adjacent* 
> elements for
> equivalence; it does not sort the input. So if your input has 
> equivalent
> elements interspersed with non-equivalent elements, you will 
> have the
> equivalent elements split into multiple runs in the output.

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.