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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Visible or hidden derivation for controlled types ?
Date: 1997/03/16
Message-ID: <dewar.858568127@merv>#1/1
X-Deja-AN: 226102555
References: <3329621A.3E9D@elca-matrix.ch>
 <mheaney-ya023680001603971555370001@news.ni.net>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-03-16T00:00:00+00:00
List-Id: <comp.lang.ada>


<<I think the general advice according to the Rational is that the derivation
be done privately.  The guideline is that clients shouldn't care whether
the type inherits from Controlled; that is an implementation detail.  If
clients really don't care, then it's an even better idea to hide the
derivation, so the client can't accidently call Initialize or Adjust.>>

I am not sure I agree, it is certainly part of the visible public
specification that the type has automatic storage collection on destruction,
which in Ada, typically means that it is controlled. 

It seems quite natural to put the Finalize in the public part, and use it
as the focal point for the documentation that provides for automatic
storage collection.

The counter argument is that the implementation might have garbage
collection, and not need the finalize, and that therefore it is indeed
an implementation detail.