Re: Not intended for use in medical,

["John G. Volan" <johnvolan@sprintmail.com>]

Robert Dewar wrote:
> 
> John said
> 
> <<So why do we have inheritance in Ada95?  Because, quite simply, it was
>   perceived by many that Ada9X would be doomed to utter extinction if it
>   did not become a fully object-oriented language.>>
> 
> This is just wrong, you like to guess about things, but you were not
> there, and so it is not surprising that your guesses bear little
> relationship to reality.
> 
> One of the things that is becoming generally agreed in programming
> languages is that you need both genericity (for parametrized abstractions)
> and inheritance (for extensible abstractions. Ada 83 had one and not the
> other, 

This is not precisely correct: Ada83 _did_ have inheritance, which has
been often overlooked.  Derived types have always inherited their
structure, and all their primitive operations (as they are now called),
from their parent types.  What is new in Ada95 is type _extension_,
which tagged types provide, along with classwide programming and dynamic
dispatching.

I make this point because it is to the credit of the Ada9X team that
they were able to achieve the goal of making Ada95 fully OO by taking
what was already inherent in Ada83 and extending it in a very natural
way, rather than encrusting the language with an entirely new construct
(e.g. class types or package types).

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