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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Ada95: at clause - 'Address
Date: 1996/10/18
Message-ID: <DzHIE5.9o8@world.std.com>#1/1
X-Deja-AN: 190418827
references: <3267958B.41C6@erols.com>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-10-18T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <3267958B.41C6@erols.com>,
Ramesh Sadasivam  <madurai@erols.com> wrote:
>In Ada95 I guess the "at clause" has been replaced with the 'Address.

The "at clause" still exists, but is considered obsolescent.
"for X use at Y;" means exactly the same thing as "for X'Address use Y;",
but the second syntax is considered preferable.  But if you have
existing Ada 83 code, there is no need to modify it to use the second
syntax.

>    ITEM_ADDRESS : SYSTEM.ADDRESS := ITEM; 

You need to make this a constant.  In your CASE 1, the address was an
'in' parameter, which is a constant, so it worked.  This is not a hard
rule of Ada, but an allowed restriction.  I think the GNAT error message
points you to the right RM paragraph.

The rule is that in portable code, if you want to say "for X'Address use
Y;", make sure Y is a constant, and that it is declared before X.

- Bob