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From: joe@petsd.UUCP (Joe Orost)
Newsgroups: net.lang.ada
Subject: Re: Ambiguous use of dereference in Ada
Message-ID: <598@petsd.UUCP>
Date: Wed, 24-Jul-85 10:41:11 EDT
Article-I.D.: petsd.598
Posted: Wed Jul 24 10:41:11 1985
Date-Received: Thu, 25-Jul-85 06:45:12 EDT
References: <38000019@gypsy.UUCP>
Reply-To: joe@petsd.UUCP (Joseph M. Orost)
Organization: Perkin-Elmer DSG, Tinton Falls, N.J.
Summary: "appropriate for the type"
List-Id: <comp.lang.ada>

In article <38000019@gypsy.UUCP> rosen@gypsy.UUCP writes:
>     ...
>     type stupid is 
>       record
>	 a: integer;
>	 b: float;
>       end record;
>     type stupid_ptr is access stupid;
>     c1, c2: integer;
>     xxx: stupid_ptr;
>  begin
>        c1 := xxx.a;		--1--
>        c2 := xxx.all.a;	--2--
>     ...

Some quotes from the bible:

	4.1.3(6)     (b) A component of a record:

	     (7)	The selector must be a simple name denoting a
			component of a record object or value.  The prefix
			must be APPROPRIATE FOR THE TYPE of this object or
			value.

	     (11)    (d) An object designated by an access value:

	     (12)	The selector must be the reserved word ALL.  The
			value of the prefix must belong to an access type.

	4.1(6)		A prefix is said to be APPROPRIATE FOR A TYPE in
			either of the following cases:

	   (7)		 o The type of the prefix is the type considered.

	   (8)		 o The type of the prefix is an access type whose
			   designated type is the type considered.

In your example, the first dereference is legal because of 4.1.3(7) & 4.1(8).
The second dereference is legal because of 4.1.3(12) & 4.1.3(7) & 4.1(7).

QED.

				regards,
				joe

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