Module-level visibility

[Nekuromento]

retard Wrote:

> Mon, 15 Feb 2010 15:48:49 -0800, Ali Çehreli wrote:
> 
> > bearophile wrote:
> >> I have shown this little program to some of my friends that program in
> >> Java/C#:
> >> 
> >> class Foo {
> >>     private int x;
> >> }
> >> void main() {
> >>     Foo f = new Foo;
> >>     f.x = 5;
> >> }
> >> 
> >> 
> >> When I say them this code compiles with D2 they usually tell me that
> >> the compiler has a bug. So I suggest Walter to ask other people, maybe
> >> at Google or else (and in this newsgroup too), if they think this
> >> feature of D2 is a good thing, before this feature is set in stone in
> >> D2 (I have no definite answer about this topic, I can't help you). If
> >> you are really sure this is a good feature, then you can ignore this
> >> post.
> >> 
> >> Bye,
> >> bearophile
> > 
> > I don't have much experience with D, but I think this feature is useful.
> > It solves the problem of giving access rights to a select few, in
> > addition to the class itself.
> > 
> > In C++, it is sometimes sought to allow some classes to have more rights
> > than the general public. For example, let the public have read access to
> > certain features, but let some classes have write access.
> > 
> > In D, that select few is the module by default, and may be extended to
> > the package.
> 
> In languages like Java/C#/Scala, there is no friend attribute. Still 
> major applications can be built. According to some OOP principles 
> accessing the internal state is often a design error. There might be some 
> efficiency issues, but other than that, I guess the large number of Java/
> C# programs clearly shows that 'friendship' is not a critical feature. 
> IMHO the implicit friendship feature inside the same module causes more 
> problems than advantages also in D.

In Delphi protection attributes behave the same as D ones. Module is commonly developed by one person, so he know what he can mess around with and what should be protected from others. So default 'friendliness' of classes within module is an advantage from my point of view, though it can lead to close coupling of classes in some cases.
Also C# has 'internal' attribute which opens access to everyone within current assembly to class members marked with it.