Re: Constructor in ADA9X

[RTOAL@lmumail.lmu.edu (Ray Toal)]

In article <3h6bno$7q8@toads.pgh.pa.us> tore@lis.pitt.edu (Tore Joergensen) writes:
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>From: tore@lis.pitt.edu (Tore Joergensen)
>Newsgroups: comp.lang.ada
>Subject: Re: Constructor in ADA9X
>Date: 6 Feb 1995 23:35:20 GMT
>Organization: University of Pittsburgh
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>DELROEUX JEAN-YVES (jydelr@vub.ac.be) wrote:
>:  I would like to know how make a constructor ( like in C++ ) in ADA9X. Is it
>: possible ?? If yes how and if not, why and how can I simulate constructors ?

>:       Thanks for your help.

>:       DELROEUX Jean - Yves

>From the Ada9x-RefManual's index:
>constructor 
>      See initialization 3.3.1(19), 7.6(1) 
>      See initialization expression 3.3.1(4) 
>      See Initialize 7.6(1) 
>      See initialized alligator 4.8(4) 
>You can find the ref.manual with a web-browser on
>http://lglwww.epfl.ch/Ada/LRM/9X/rm9x/

One thing about C++ constructors that I haven't really been able to
simulate are the fact that they are NOT inherited in C++ (which is
useful.)  Consider:

package Shapes is

  type Shape is abstract tagged record;
  procedure Display (S; Shape) is abstract;

  type Circle is new Shape with private;
  function Make_Circle (C: in out Circle; Radius: Real) return Circle;
  procedure Display (C: Circle);

  type Rectangle is new Shape with private;
  function Make_Rectangle (R: in out Rectangle; Width, Height: Real)
                                        return Rectangle;
  procedure Display (R: Rectangle);

  type Square is new Rectangle with private;
  function Make_Square (S: in out Square; Side_Length: Real) return Square;
  procedure Display (S: Square);

  type Triangle is ....

private

   ...

end Shapes;

You will get the error message "Make_Rectangle must be redeclared for
type Square..."  Does anyone know a nice, clean workaround?

Ray Toal