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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Overring function and its returned type
Date: Sat, 10 Nov 2012 03:35:17 +0100
Organization: Ada @ Home
Message-ID: <op.wnjdg3vfule2fv@cardamome>
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Date: 2012-11-10T03:35:17+01:00
List-Id: <comp.lang.ada>

Le Sat, 10 Nov 2012 01:28:54 +0100, Yannick Duch=C3=AAne (Hibou57)  =

<yannick_duchene@yahoo.fr> a =C3=A9crit:
> What's nice with the second attempt, is that it works

It works, but it's unsafe on the long=E2=80=91run: if there are, one of =
the  =

preconditions of the inherited `F` must be reported to the other `F`, an=
d  =

the same with postconditions, except you have to report them all. This i=
s  =

too risky, as something may be forgotten and the language does not help =
 =

here. Even more risky if maintenance occurs on the inherited `F` in an  =

ancestors type, and some predicates are changed, or worst predicates add=
ed  =

while there were none.

Even if annoying, the only safe way is really the initial one, that is t=
o  =

just have one `F`, the inherited one overrided, with an added  =

postcondition and an explicit checked type conversion at call places  =

(which may be removed in the future if ever a day Ada starts to supports=
  =

this).

-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity