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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: Gnat For use at Question
Date: 1996/07/11
Message-ID: <dewar.837096600@schonberg>#1/1
X-Deja-AN: 168309473
references: <4s2eb5$qt6@masala.cc.uh.edu>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada
Date: 1996-07-11T00:00:00+00:00
List-Id: <comp.lang.ada>


Spasmo asks why GNAT rejects:
"Some_Array : String(1..4000);
for Some_Array use at 16#bbbbb#;"

GNAT rejects this because it is plainly illegal. Address, in accordance
with the implementation ad vice in the Ada 95 RM is a private type in
GNAT, and you obviously can't use an integer literal as the value of 
a private type.

Look up the facilities in System.Storage_Elements to find out how to
do what you want. Rememeber that GNAT implements the restriction that
the address expression must be a prior defined constant, so you cannot
just use To_Address directly, since a call to To_Address is not static.
So you want something like:

	Some_Array_Address : constant Address := To_Address (16#bbbb#);
        Some_Array : String (1 .. 4000);
        for Some_Array'Address use Some_Array_Address;

P.S. since almost certainly what you have in mind is overlaying the
display buffer, it would be much neater to have an Ada variable with
more structure (something like a two dimensional array of records
containing an attribute which is a packed record and a character).