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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Array Help?
Date: Wed, 29 Feb 2012 13:24:10 -0500
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Date: 2012-02-29T13:24:10-05:00
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Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

> Doesn't that preclude slices that don't start at 'First?

Yes.

> Supposing your declarations, can you call
>
> procedure Foo (Param : in out Integer_Array);
>
> like this:
>
> declare
>    A : Integer_Array (1 .. 10) := (others => 0);
> begin
>    Foo (A (3 .. 8));
> end;
>
> ?

That will raise C_E.  IMHO, that's a language design flaw -- inside
Foo, Param'First ought to be 1.  The fact that Foo can see that
it came from a slice is a leak of abstraction.

The fact that arrays slide in many situations is proof that
people don't really care too much about the bounds -- they
care about the length.

Anyway, slices aren't really all that useful -- for many array types,
you don't need them at all.  And slices as l-values, as in your
example, are quite rare, because you really want to be able to
change the length of the slice, if you want to change it at all.
The following won't work:

    X : String := "Hello, world.";

    X(1..5) := "Goodbye"; -- raises C_E

- Bob