Re: Teaching C/C++ from Ada perspective?

[Maciej Sobczak <see.my.homepage@gmail.com>]

> Make the other package a child.

It's cheating. :-)
The problem is - the "private" in Ada package spec does not correspond to "private" in C++ classes, but rather to "protected". You can extend a C++ class with a derived class and access protected stuff from there - this is the equivalent of creating a child package in Ada in order to access the not-so-private parts from the parent.
In other words, this Ada idiom is replicable in C++ with the use of "protected" parts.

It is the "private" in C++ that has no equivalent in Ada.
That is:

class MyCppClass
{
public:
    // ...
    // this is what you have in the public part of Ada spec

protected:
    // ...
    // this is what you have in the "private" part of Ada spec,
    // you can access this part from derived classes or children packages

private:
    // ...
    // no, you don't have this level of privacy in Ada (!)
    // and definitions in your package body are not exactly equivalents
};

> I often have packages with procedures declared in the private part for
> the benefit of children (only).

As shown above, C++ programmers put this kind of stuff under the "protected" tag.

When it comes to friends, they are implemented in Ada in terms of putting multiple types within the same package, so that they can see each other. I admit that I like this idiom more than than the friendship in C++, even if friends are more flexible (they can make much longer spans, but I would say it is a privacy equivalent of goto, with the same long-term consequences).

-- 
Maciej Sobczak * http://www.inspirel.com