On Tuesday, 22 November 2022 at 21:45:29 UTC, []() {}() wrote:
On Tuesday, 22 November 2022 at 21:00:58 UTC, []() {}() wrote:
"Being able to declare a “friend” that is somewhere in some
other file runs against notions of encapsulation." (This is the
motivation for that article it seems).
I completely disagree with the assertion.
C++ Friend notion does not, not by any means, run against the
notion of encapsulation.
Sure, it expands the perimeter (i.e. it puts a door in the
wall).
But, and this is my point, there is a guard standing at the
door. And that guard knows who has been authorised to pass
through it. The encapsulation remains. Only its perimeter has
been expanded.
One could argue that D's approach is just that. It expands the
perimeter to the module level. But there's no guard at the door
in D.
Surely, this 'let anyone pass through' design, decreases
encapsulation? How could it possibly increase encapsulation, as
claimed, by the author of that article?
If there were a means in the language for controlled sharing
within a module, *that* would increase encapsulation.
The module is the capsule. D is simply not interested in building
a capsule around a class. D does not let "anyone" pass through,
it lets "anyone in the module" pass through, because the module
is the wall. I think this is a stronger concept of encapsulation
than C++ friends because the encapsulation is lexical rather than
just declarative.
