Re: [boost] [yap] Review

Subject: Re: [boost] [yap] Review
From: Rob Stewart (rstewart_at_[hidden])
Date: 2018-02-14 21:48:21

On February 14, 2018 4:04:12 PM EST, Zach Laine via Boost <boost_at_[hidden]> wrote:
> On Wed, Feb 14, 2018 at 2:44 PM, P F <pfultz2_at_[hidden]> wrote:
> 
> >
> > If there are advantages to using mp_assign, maybe this extra noise
> in a
> > few places is worth it.  I still have no idea what the mp_assign
> advantages
> > are though.
> >
> >
> > The point is to be able to get rid of `::` at the beginning in
> > `BOOST_YAP_USER_UNARY_OPERATOR_MEMBER(logical_not, ::user_expr)`. If
> the
> > user forgets those, you need to have a clear way to tell the user
> they need
> > to add them, because it may not be obvious from the compiler error
> without
> > understanding the implementation details.
> >
> > One way to solve this is to avoid it altogether by not passing a
> template,
> > which you can try to utilize something like mp_assign.
> >
> > Another possible solution may be to add a static_assert with a
> message
> > like “you are passing a type instead of template, you may need to
> prepend
> > :: to the parameter to this macro". I think you can use function
> > overloading to distinguish between a type and a template, but I am
> not
> > sure.
> >
> 
> Ah, I get it now, thanks.
> 
> I think I'd rather document better that the :: is required, as opposed
> to
> doing more template chicanery.  This is both because I want to keep
> compile
> times low, and because I don't want to make something that might be
> brittle
> in ways I don't fully understand.  I'm a metaprogrammer of only
> moderate skill.

You could prepend :: in the macro.

--
Rob
(Sent from my portable computation device.)