Re: Copying rows in a two dimensional array.

[Jerry <lanceboyle@qwest.net>]

On Feb 2, 1:52 am, Jean-Pierre Rosen <ro...@adalog.fr> wrote:
> Jerry a écrit :> I've never understood why Ada does not allow slicing in
> > multidimensional arrays. What are the safety issues involved? And how
> > is it safe to force the programmer into ad hoc methods?
>
> One-dimensional slices are simple and efficient. Multidimensional slices
> are a can of worms.
>
> I guess you are thinking about rectangular slices. But why stop there? A
> slice comprising the main diagonal and the diagonal above and below can
> be very useful for some calculations. Or a slice which is the triangular
> part of the upper half...
>
> AFAICT, Fortran-99 does provide this - and the syntax is so complicated
> that nobody uses it. And implementation is also a nightmare.
>
> When designing a programming language, you have to stop at some point.
> The ratio (cost of implementation) / usefulness is a good measure for
> this. I think the ratio was simply to high for this feature.
>
> --
> ---------------------------------------------------------
>            J-P. Rosen (ro...@adalog.fr)
> Visit Adalog's web site athttp://www.adalog.fr

Well, yes, I was thinking of rectangular slices. No doubt the (cost of
implementation) / usefulness is high (and usage difficult) for non-
rectangular parts, but that is far less common than rectangular parts.
Python, Matlab/Octave, Igor Pro... all pull it off without too much
hassle (although Python asks you to imagine addressing the array by
the "cracks" between elements, as I recall--probably a disease of C-
style counting).

Jerry