Re: Design by contract and control inversion

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

Le Fri, 02 Nov 2012 09:59:53 +0100, Yannick Duchêne (Hibou57)  
<yannick_duchene@yahoo.fr> a écrit:
>      -- abc-sets-base.ads
>
>      generic
>
>         type Element_Type is private;
>         type Cardinal_Type is (<>);
>
>      package ABC.Sets.Base is

As it was posted, a note on this.

The `Cardinal_Type` is just a discrete type here, which may looks  
over‑generalized to somebodies, and indeed the standard Ada containers use  
a range type instead. The discrete type is enough even for a  
implementation, but if you wish to add pre/post condition on the  
cardinality in the specification, then a discrete type becomes a burden  
(unless you enjoy Peano arithmetic a lot). There's no real rule here, that  
just depends… Just still one thing: that's always OK to change from the  
discrete type to a range type, but not the opposite; so that may be better  
to start with the discrete type and change this later if required.


-- 
“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