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From: Brian Rogoff <bpr@shell5.ba.best.com>
Subject: Re: GNAT controlled types
Date: 1998/01/28
Message-ID: <Pine.BSF.3.96.980128145319.2158A-100000@shell5.ba.best.com>#1/1
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Date: 1998-01-28T00:00:00+00:00
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On Wed, 28 Jan 1998, Tucker Taft wrote:
> 
> The decision to base controlled types on type extension was an attempt
> to ensure a relatively straightforward implementation, where the
> root controlled type would contain links for inserting the controlled
> object on a linked list.  Ultimately, other considerations (such as
> "mutable" discriminated types) pushed us to abandon the 
> links-through-the-object implementation model in our Ada 95 front end,
> but I believe other compilers have taken advantage of the type
> extension approach.

Could you elaborate a bit more on why you switched implementation models, 
and how your front end implements them now? I used to hold the same view 
as Nick, i.e. that this conflation of Controlled-ness and tagged-ness was
a flaw, and I changed my mind after trying to figure out alternative
approaches. 

-- Brian