most elegant functional way to make a histogram

[Laeeth Isharc via Digitalmars-d-learn]

On Monday, 24 August 2015 at 09:50:41 UTC, yawniek wrote:
> On Friday, 21 August 2015 at 21:08:25 UTC, Laeeth Isharc wrote:
>> I guess this kind of thing will do:
>> upRangeHighs.each!((ref a)=>(++histogram[a][0]));
>    	
>
>   int[] arr = [5,1,2,2,3,4,5,5,5];
>   int[int] histo;
>   arr.each!( a => ++histo[a]  );
>   writeln(histo);
>
> this works

Thanks v much for suggestions, everyone.  In the end I just went 
with something like the above.