Re: Idiom for a class and an object in Ada

[Jeffrey Carter <spam@spam.com>]

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++; it's not needed in Ada.

-- 
Jeff Carter
"Ada has made you lazy and careless. You can write programs in C that
are just as safe by the simple application of super-human diligence."
E. Robert Tisdale
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