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From: maa@liacc.up.pt (=?ISO-8859-1?Q?M=E1rio_Amado_Alves?=)
Newsgroups: comp.lang.ada
Subject: Re: MI in Ada 200X (was: Suggestion for Ada 200x - Interface
 inheritance)
Date: 29 May 2003 05:06:38 -0700
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""Everybody wants class MI. The reasons it was left out of Ada 95 and
83, the cons, are weaker than the pros.""

"Convince me :-) Seriously what are the pros and cons of MI." (Preben)

The cons include the (aledged) "implementation burden" (Tucker Taft).

"I must not be everybody.  Ada currently supports the mix-in model of 
multiple inheritance." (Robert)

Sure. I was talking about *class* MI. (Tucker calls it "linguistic".)

The pros include "naturalness" of expression, occuring both at
creation

  type Child is new Mother, Father;

and at selection

  Do (A_Child.Mother_Feature)
  Do (A_Child.Father_Feature)

And sure it's not "everybody" who wants it. But many folks do and
recurrently voice it. It's an unsettled issue. Kind of as exceptions
as tagged types (AE'2001). I guess it's Ada class wide programming
felt as its most natural OO idiom.

I wouldn't mind having it as an extension defined in a specialized
annex. There is already a number of 'standard' Ada subsets (DSA,
SPARK, Kernel Ada). Why not a superset?

  pragma Multiple_Inheritance (Child); -- :-)