Am Sa., 6. Juli 2019 um 18:36 Uhr schrieb Jonny Grant via
Std-Proposals <std-proposals_at_[hidden]>:
>
>
>
> On 06/07/2019 17:17, Jake Arkinstall via Std-Proposals wrote:
> > We've had many a discussion on this and it's a bit... fiddly. I still
> > hold that with a type interface as good as we have, there's no need for
> > named parameters as long as we don't have people going around writing
> > functions called "func" that take two booleans.
>
> It would be similar with widget.init(filename, true, false) wouldn't it?
>
> My only workaround for this is for every method to provide in the class
> namespace a widget::debug_on etc, so can then call:
>
> widget.init(filename, widget::debug_on, widget::log_off);
>
>
> > However, that's just my take. There are good examples of where it
> > becomes useful, and on the other hand there are examples of where it
> > encourages lazy, difficult to optimise API design with bag functions.
> > There are questions about mangling (unless you tie it to the header),
> > questions about compatibility, questions about collision handling, and
> > questions about ordering requirements. I believe the last conversation
> > ended with an idea about treating function parameters as a struct with
> > defaults and using C++20's designated initializer syntax. Now we know
> > designated initializers have made it into the next iteration of the
> > language, that approach seems the most promising.
>
> Could you share an example of where it encourages lazy or difficult to
> optimize api design please.

Pretty much every function taking a boolean (or any fundamental type
for that matter) is lazy API design. In your example you could've also
used two separate scoped enums - one for debugging and one for logging
- instead of adding boolean constants into a namespace. That way the
API enforces readable code at every call site. That doesn't solve
optional parameters though.

>
> C99 has had designated initializers for a long time I recall. How would
> this work in C++ for this issue?
> Would we need to provide two versions of the same method?
>
> Cheers, Jonny
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