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From: vladimir@speedy.intrepid.com (Vladimir Vukicevic)
Newsgroups: comp.lang.ada
Subject: Re: Type t is MOD c???
Date: 07 Feb 1995 07:16:28 GMT
Organization: Intrepid Technology, Inc.
Message-ID: <VLADIMIR.95Feb6231628@speedy.intrepid.com>
References: <3h5bei$npp@nyheter.chalmers.se>
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In-reply-to: Magnus Hakansson's message of 6 Feb 1995 14:24:18 GMT
Date: 1995-02-07T07:16:28+00:00
List-Id: <comp.lang.ada>

In article <3h5bei$npp@nyheter.chalmers.se> Magnus Hakansson
<z94magh@mtek.chalmers.se> writes:
> This probably a very simple question when you know the answer, but
> it is causing me some troubble. In "system.ads" there is a
> declaraton:
>
> type Address is mod Memory_Size;
>
> and I want to know how to assign a specific address to a pointer.
> How do I do? What is the syntax for an "address"? Is there any
> hidden packages avilable for accessing certain bytes of the memory
> of my PC, or is there any other tricks I don't know?
>
> Can anyone help me on this subject?

You would do something like:

with System.Storage_Elements;
package Q is
	X : Integer;
	for X'Address use System.Storage_Elements.To_Address (16#ffff#);
end Q;

to access the Integer at address 16#ffff#.

The type Address is left as implementation-defined in the standard; in
GNAT, it's private. The 'Address attribute rep clause takes a
System.Address, so you have to use the functions in System.Storage_Elements
to convert an integer to an Address. (See RM9X5.0 13.3(10), 13.7, 13.7.1)

	- Vladimir