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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: About String
Date: Sun, 15 Jun 2008 15:38:08 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2008-06-15T15:38:08-04:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> On Sun, 08 Jun 2008 17:19:11 -0400, Robert A Duff wrote:
>
>> Maciej Sobczak <see.my.homepage@gmail.com> writes:
>> 
>>> After all, with the possibility to initialize the new variable with
>>> arbitrarily complex expression (including function call), this is
>>> already the case and the whole declare-begin-end block is just
>>> reflecting some artificial separation.
>> 
>> I agree.  I suppose it comes from Pascal, where declarations and
>> executable code are completely separated.  It makes no sense in
>> Ada, where declarations are just as executable as statements.
>
> I disagree. I think it does make sense because it clearly defines the scope
> of the declared variable. Expression (result) /= named object. And
> reversely, if you don't need the variable, you are free to put expressions
> anywhere outside the declaration part.

If Ada allowed:

    for I in A'Range loop
        X : constant Character := F(A(I)); -- Not Ada!
        Do_Something(X);
    end loop;

the scope of X is clear -- it's the entire loop body.

    for I in A'Range loop
        declare
            X : constant Character := F(A(I));
        begin
            Do_Something(X);
        end;
    end loop;

does not clarify (in my opinion).  It just adds noise.

You could still say:

    for I in A'Range loop
        begin
            X : constant Character := F(A(I)); -- Not Ada!
            Do_Something(X);
        end;
        Do_Something_Else;
    end loop;

in my circus, if you want to further limit the scope of X
(to smaller than the whole loop body).

- Bob