Why do private member variables behaved like protected in the same module when creating deriving class?

[Walter Bright]

On 10/26/2018 12:45 PM, David Gileadi wrote:
> It certainly is deliberate, though.

Just to confirm, yes it is deliberate.

> I believe it may have been inspired by C++'s 
> "friend" declarations.

That is correct, as well. C++ friend is a hackish thing, with consequences in 
appearance, name lookup and scope. Being able to declare a "friend" that is 
somewhere in some other file runs against notions of encapsulation.

Java's notion of one class per module is a bit too restrictive, as one may 
desire a set of closely interrelated classes that encapsulate a concept, and 
those should go into a module.

C++ files tend to be accumulations of lots of stuff, often unrelated. 
Translations of C++ code to D (such as dmd is) reflect that as well. Phobos 
suffers from that, too, it's hard to break away from it.

D modules should reflect a more encapsulated approach, which suggests an 
idiomatic D program should consist of a lot more, and smaller, modules than a 
typical C/C++ organization.

---

I spent a lot of time learning programming in the 80's on floppy disks. Files 
took a long time to look up and load, so one tended to organize a program as a 
smaller number of larger files. Such were faster to browse and faster to 
compile. These effects are insignificant today, but old habits linger.