Ranges/algorithms for aggregation

[bearophile]

Luís Marques:

> 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?

I don't know any, how is it supposed to know where to group 
items? Usually you build an associative array for that.

Bye,
bearophile