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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Array Help?
Date: Wed, 7 Mar 2012 18:08:28 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2012-03-07T18:08:28-06:00
List-Id: <comp.lang.ada>

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccpqcxrzj2.fsf@shell01.TheWorld.com...
...
> Actually, I just realized there's a workaround for the slice problem.

Yes, as I just posted. I guess I should have read further before answering.

> The following does not raise any exception.
>
>  procedure Array_Test is
>
>     type Integer_Array is array (Positive range <>) of Integer
>       with Dynamic_Predicate => Integer_Array'First = 1;
>
>     procedure Foo (Param : in out Integer_Array) is
>     begin
>        null;
>     end Foo;
>
>     A : Integer_Array (1 .. 10) := (others => 0);
>
>     subtype Slide is Integer_Array(1..6);
>  begin
>     Foo (Slide(A (3 .. 8)));
>  end Array_Test;
>
> But that's kind of tricky; I wouldn't do that without copious
> comments.  And some constants or something to avoid violating
> the DRY principle.

Maybe it's tricky, buit I've used it a lot, especially inside of things like 
Ada.Strings.Fixed (and in my spam filter, which tends to do direct string 
manipulations because it's usually easier to do that than to figure out what 
Ada.Strings.Fixed function does 80% of the job [none of them ever seem to do 
the whole job] and then figure out how to do the rest afterwards). But 
typically, "Slide" uses bounds derived from whatever you're going to pass 
(usually, "3" and "8" above are local variables anyway):

  declare
    L : Natural := 3;
    R : Natural := 8; -- These are usually calculated from the other code 
nearby.

    subtype Slide is Integer_Array(1..R-L+1);
  begin
     Foo (Slide(A (L .. R)));
  end;

Feel free to turn this into a "gem" if you're so inclined. :-)

                          Randy.