Re: Why no Ada.Wide_Directories?

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

Le Sat, 22 Oct 2011 09:54:07 +0200, Dmitry A. Kazakov  
<mailbox@dmitry-kazakov.de> a écrit:
>> Conclusion: the interface could not remain the same, and different
>> interface, means different type.
>
> Here you confirm that LSP does work. But Ada does not base its type  
> system
> on LSP. There cannot be any usable LSP-conform type system.
It actually do. But it will never with a broken design, obviously. With  
the above example of sub‑typing a container for a subtype element type,  
the trouble does not come with Ada, but with the merge of two interfaces:  
input interface and output interface. It's a rule of thumb for me, to  
separate both, because after some experiences, I've learned sooner or  
later, you face troubles if you do not distinguish both (*). If you have  
two interfaces, one for input and one for output, there is no more  
trouble, you can subtype the Input interface to follow an element subtype.  
If you don't want to separate both, then you just can't subtype this way.  
You have to make a choice, and that's not Ada's fault, that's the domain's  
“fault”.

Although Jean-Pierre underlined they are with Ada, some matters which are  
in practice above some others (which is true and OK to notice), nothing in  
Ada prevents you from using the good design, even if that design does  
match Ada niches and typical use cases (you may just have to not tell  
anyone, cheese).

(*) I like to redesign sometime, with a read only abstract T1 and a  
concrete derived read/write T2.

If you really believe Ada subtypes, *as Ada allows to use it*, does not  
conform to the substitution principle, can you provide an example ?  
Personally I don't see a trouble if the language does not allow you to do  
something it would not be able to handle. You know… better not run  
anything at all, than running an erroneous thing.

Please Dmitry, could write down once a whole, all you comments about Ada.  
Even do it with a funny title, kind of “Ada criticisms (and _proposals_)”  
if you feel it. At least this would help to follow the story, because  
that's easy to forget what was already said and what was not, along with  
rationales and examples… I have a strange feeling of repeating myself,  
sometime, when I reply to you when you complain. Also, this would be an  
opportunity for better formalization of your comments. I don't enjoy talks  
which too much seems to be about taste when the subject is a rather formal  
thing (the language) and also when the subject is something into which  
many people invested a lot. Your paper could also be opened for comments  
(just like Ada do with its definition). An opportunity for better, longer  
and clearer clarifications in a single reference place would be nice.

-- 
“Syntactic sugar causes cancer of the semi-colons.”  [Epigrams on  
Programming — Alan J. — P. Yale University]
“Structured Programming supports the law of the excluded muddle.” [Idem]
Java: Write once, Never revisit