Re: What would you like in Ada202X?

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

Le Wed, 25 Apr 2012 20:14:59 +0200, Jeffrey Carter  
<spam.jrcarter.not@spam.not.acm.org> a écrit:

> On 04/25/2012 02:09 AM, Georg Bauhaus wrote:
>>
>> 0) Which features do you think can be dropped from Ada?
>
> Interfaces
> Tagged types (but retaining finalization for record types)

Less radical, I was wondering about some redundancies between both.

> Child packages with visibility of their ancestors
>
> These would return Ada to its original vision as a language for  
> programming by composition.

You mean visibility of the ancestor's private part to the child package,  
is that it?

Programming by composition welcome means to express worlds and domains  
with shared internal secrets. On the other hand, package are king of  
structure, and Ada's tagged type does not provide visibility of the  
internals of one's ancestor. On the third hand (alien talking here),  
tagged types don't have this, precisely because it's provided by package  
hierarchy.

Imagine a simple case: a serialization of some private object type, with  
multiple codecs. I instinctively make each codecs, a child package of the  
package defining the serialized type, so that they can build an instance  
of type. Or else, you would have to expose to the big world, methods  
intended for serialization only, and serialization is often related to the  
internal representation of the serialized item (although not required).  
Can't give an easy example, but I also believe this would make some  
bindings more difficult.

I feel to anticipate removing child package with visibility to their  
ancestor's private part, would force people to expose too much in their  
specifications, or worst, to fake this feature using export/import behind  
the scene.

But I may be wrong, and will more deeply think this case later. I'm so  
much made to this, and can't easily think without it. For the time, I have  
some personal pending stuff to do a later day, with 5 levels of child  
package all with visibility to their parent's privates :-P .

-- 
“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