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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: How to get Ada to ?cross the chasm??
Date: Tue, 1 May 2018 17:17:58 -0500
Organization: JSA Research & Innovation
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Xref: reader02.eternal-september.org comp.lang.ada:51894
Date: 2018-05-01T17:17:58-05:00
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"Paul Rubin" <no.email@nospam.invalid> wrote in message 
news:87in88m43h.fsf@nightsong.com...
...
> A cleaner approach imho is immutable data passed by reference (this is
> how most of functional programming works).  It's not really feasible to
> code in that style in Ada, as far as I can tell.

Why do you say that? It's not done that often, but plenty feasible: an 
immutably limited type is always passed by reference, and constants don't 
change (with a few technical exceptions easily avoided if you wish), so one 
can easily use limited records in that way:

      type Data is limited record ...

      function Munge (Obj : in Data) return Data;

The problem comes (in any design) when you start using references rather 
than the actual objects; my point was that you need to minimize references 
(in all forms) to really reduce these issues. A reference necessarily leads 
to dangling references or methods to avoid such -- and that way leads to 
madness (or GC, roughly equivalent ;-).

Claw uses references in only a very few targetted situations; almost 
everything in the GUI is constructed by aggregation. Works great (even if a 
bit stale since it is for Win32).

                                    Randy.