On Saturday, 12 July 2025 at 23:55:39 UTC, Ali Çehreli wrote:
On 7/11/25 11:36 PM, Bienlein wrote:
> Unhappily class MessageBox is private and therefore cannot be
reused.
Ah! :) That's one more data point against 'private', that
little feature that helps with nothing. I don't know what
language invented it but I wouldn't be surprised if it came to
D from C++.
C also has private. It's called `static`. Or sometimes `pImpl`
(for types).
The only thing 'private' achieves is this: You don't want your
users to be disappointed when they go out of their way to use
features that they are advised not to use, and those features
behave differently in the future. Really? That never happens.
Well, if it indeed happened ever, the user went out of their
way to be surprised, didn't they?
No, that is not what private is for.
Private means you get to define the API of your code. If you
don't have it, anyone can come in and change anything and you
can't do anything about it. Testing your code in a production
environment is impossible, because *anyone can do anything*.
Invariants can never be trusted. Nobody can reason about the code
in any sensible way. Private data is very important when properly
used.
In this case, the fact that `MessageBox` is unusable to a user is
*not* the fault of `private`. It's just that the author happened
to use the `private` attribute to prevent others from using it.
There are other ways, and without private, they likely would have
used one of those ways.
We have `std.internal` and `core.internal`. Perhaps the better
mechanism than using `private` is to put it in here. Then at
least it's known to be an internal detail, but still usable by an
adventurous user.
Note, I have also recently run into some [foolishness in the
library WRT private
symbols](https://github.com/dlang/dmd/blob/e0cf19144f2afed531cc2f40eee7e051994d4e98/druntime/src/core/thread/threadbase.d#L73-L87)
Just like anything, it can be misused.
-Steve
