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NNTP-Posting-Date: Thu, 15 Aug 2019 11:45:38 -0500
Subject: Re: The answer to "Can Ada replace FORTRAN for numerical computation?
Newsgroups: comp.lang.ada
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Date: Thu, 15 Aug 2019 10:45:37 -0600
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Xref: reader01.eternal-september.org comp.lang.ada:57065
Date: 2019-08-15T10:45:37-06:00
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Randy Brukardt wrote:
> "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.
> 
> 
I agree that arrays would probably work better as containers, but array 
slices are very handy in a number of cases when you need to copy part of 
an array or restrict the view of the array.  But then slices would 
probably work better as container functions too.