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From: kevin.cline@gmail.com (Kevin Cline)
Newsgroups: comp.lang.ada
Subject: Re: Idiom for a class and an object in Ada
Date: 21 Oct 2004 12:31:00 -0700
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Date: 2004-10-21T12:31:00-07:00
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Jeffrey Carter <spam@spam.com> wrote in message news:<woEdd.2702$%h1.1164@newsread3.news.pas.earthlink.net>...
> Matthew Heaney wrote:
> 
> > For reasons I can't fathom, many Ada95 developers still have a very
> > Ada83 mindset.
> 
> That's because Ada 83 was a very good language, and the idioms that were 
> good for it are still good.
> 
> > This is the canonical idiom in C++ for controlling instance creation:
> > 
> > class C {
> > public:
> > 
> >    static C* make( /* ... */ );
> >    static void free(C*);
> > 
> >    void f(); //whatever
> > 
> > private:
> > 
> >    C();
> >    C(const C&);
> > 
> >    ~C();
> > 
> >    C& operator=(const C&);
> > };
> > 
> > Here, the ctor (and dtor) is declared as private, so the only way to
> > make a C object is by calling factory function C::make().
> > 
> > This has a direct translation into Ada95:
> > 
> > package P is
> > 
> >    type T (<>) is limited private;
> > 
> >    procedure Op (O : in out T);
> > 
> >    type T_Access is access all T;
> > 
> >    function New_T (...) return T_Access;
> 
> And this is why C++ is never a good guide to how to do things in Ada. 
> The pointer may well be needed in C++;

Not in this case.

  class AD_Converter
  {
  private:

    AD_Converter(int line) {}
  public:
    static AD_Converter Noise;
  };

  AD_Converter AD_Converter::Noise(17);