Reducing an array

[monarch_dodra via Digitalmars-d-learn]

On Friday, 18 April 2014 at 20:27:20 UTC, Steven Schveighoffer 
wrote:
> Note also that what it returns is not an array, but a lazily 
> iterated range over the array. If you want another array, this 
> is the code I would use:
>
> arr.sort();
> arr = arr.uniq.array();
>
> -Steve

Out of curiosity, if the requirement was to *also* preserve 
ordering (eg: remove all non-first elements), how would you go at 
it?

[2, 1, 1, 3, 2, 3] => [2, 1, 3];

Maybe std.algorithm's `makeIndex` would help here?

Bonus points for doing it inplace.