Re: Returning ranges from a function (was: How to loop (elegant) throug a vector ?)

[Stefan Bellon <bellon@software-erosion.org>]

On Sun, 22 Jun, Maciej Sobczak wrote:
> On 20 Cze, 19:12, Stefan Bellon <bel...@software-erosion.org> wrote:

> >    for I in Get_Range'Range loop
> >       Do_Something (I);
> >    end loop;
> >
> > It's not as elegant as I wished (because of the additional 'Range),
> > but it is simple and light-weight enough to be usable.
> 
> As far as I can tell, it creates the physical array that might not be
> necessarily optimized out by the compiler. You need to store it
> somewhere.

You need to store the two words for First and Last (or First and
Length). And indeed, this is what GNAT does. The 'Size of the array
object returned is two words in size.

> It would be nicer to return a "range" that is not dependent on memory
> constraints. See xrange in Python.

I think you cannot get smaller than the two words. The question is
whether this optimisation (for 'Size use 0) can always be guaranteed.

-- 
Stefan Bellon