Re: Overring function and its returned type

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Sat, 10 Nov 2012 01:28:54 +0100, Yannick Duchêne (Hibou57)  
<yannick_duchene@yahoo.fr> a écrit:
> What's nice with the second attempt, is that it works

It works, but it's unsafe on the long‑run: if there are, one of the  
preconditions of the inherited `F` must be reported to the other `F`, and  
the same with postconditions, except you have to report them all. This is  
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 added  
while there were none.

Even if annoying, the only safe way is really the initial one, that is to  
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).

-- 
“Syntactic sugar causes cancer of the semi-colons.” [1]
“Structured Programming supports the law of the excluded muddle.” [1]
[1]: Epigrams on Programming — Alan J. — P. Yale University