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From: Cyrille <comar@eu.adacore.com>
Newsgroups: comp.lang.ada
Subject: Re: on using array index, vectorized operation
Date: Sun, 27 Mar 2011 13:01:20 -0700 (PDT)
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Date: 2011-03-27T13:01:20-07:00
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On Mar 27, 3:31=A0am, "Nasser M. Abbasi" <n...@12000.org> wrote:
> Hello;
>
> Many times I need to operate on an array using an index
> by doing some operation on the index itself as a variable
> (such as shifting for example).
>
> This below is a very simple example of what I mean.
>
> Given an array A, I might want to do
>
> A(i-1) :=3D A(i) =A0 =A0----------- (1)
>
> where 'i' above is a variable which contain in it some index
> locations to use to index into the array A.
>
> In Ada, I can do the above, but I am a little clumsy in doing
> it. I know I can use array slicing as in =A0A(1..4) :=3D A(2..5),
> but wanted to do it when the index itself is a variable, as in (1)
> above. Since in other cases, I have to do more operations on the index
> itself, and so it needs to be in a variable.
>
> This is what I tried so far, and my goal to see if I can
> shorten this more:
>
> ------------------------
> procedure t is
> i: constant array (1..4) of integer:=3D(2,3,4,5);
> A: array(1..5) of integer :=3D (10,20,30,40,50);
>
> begin
> =A0 =A0--A(2..5) :=3D A(1..4);
> =A0 =A0--A(i-1) :=3D A(i); =A0--error
>
> =A0 =A0A(i(1)-1..i(4)-1) :=3D A(i(1)..i(4));
> end t;

you can write:

   A(A'First+1 .. A'Last) :=3D A(A'First .. A'Last-1);