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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: The answer to "Can Ada replace FORTRAN for numerical computation?
Date: Wed, 24 Jul 2019 18:45:26 -0500
Organization: JSA Research & Innovation
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Xref: reader01.eternal-september.org comp.lang.ada:56933
Date: 2019-07-24T18:45:26-05:00
List-Id: <comp.lang.ada>

"Lucretia" <laguest9000@googlemail.com> wrote in message 
news:28590d5c-d5f0-4322-9aa4-e1bb92419db3@googlegroups.com...
...
> Something like:
>
> M2 := M4 (1, 1 .. 2, 2); -- Makes a copy into the Matrix 2x2 type from a 
> 4x4.

This is no problem, of course. What is a problem is the fact that one can 
assign into these things and (especially) pass them as "in out" parameters. 
That causes overhead for all parameter passing of arrays, whether or not a 
multidimensional slice is ever actually used (the compiler cannot assume 
that array components are contiguous).

Array slices is one of the features I would remove from "Better Ada". Most 
of their utility comes from strings, and (modern) strings are not arrays in 
the first place. (I'd also get rid of arrays as a built-in type, making them 
a form of container.) A side-effect of that would be to get rid of the 
continuing discussion of this "obvious" extension that is way too expensive 
to have in Ada (or any language, for that matter). Subprograms can easily 
provide the "cheap" functionality, and no one really intends to use 
expensive code anyway.

                                       Randy.