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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: maintenance of overriding subprograms
Date: 1997/09/07
Message-ID: <EG54sG.D2F@world.std.com>#1/1
X-Deja-AN: 270475504
References: <340C2EA5.B9F@gsfc.nasa.gov> <dewar.873460404@merv>
 <341065D7.4D41@gsfc.nasa.gov>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-09-07T00:00:00+00:00
List-Id: <comp.lang.ada>



In article <341065D7.4D41@gsfc.nasa.gov>,
Stephen Leake  <Stephen.Leake@gsfc.nasa.gov> wrote:
>However, in addition to the maintenance problem (I had a hidden
>requirement :), I would like the source to give more immediate
>indication that we are intending the subprogram to override a parental 
>one (and the others in the same spec do NOT). ...

If I were designing a new language from scratch, I would probably do
this (that is, give some syntactic indication of the difference between
overriding vs. not overriding).  It doesn't seem easy to fit it into Ada
in a clean, simple way.  In particular, I don't like these suggestions:

>... The presence/absence of
>"new" or "pragma Confirm_Override" makes this clear. 

To me, "new" means "NOT overriding" -- that is, this subprogram
represents a *new* capability not available for the parent type, as
opposed to merely overriding an old capability.

I find the pragma idea to be in bad taste -- pragmas shouldn't have such
a strong effect on high-level semantics.

>...I think it makes
>the source easier to read; one does not have to lookup all the primitive
>parental procedures (a good tool would help, of course). This can be
>done with comments, but those can get out of sync.

Well, I suppose OOP-style programming is pretty hopeless without some
sort of tool that can show you the complete interface, with all the
inherited stuff included.

- Bob