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From: Alexander Grund (alexander.grund_at_[hidden])
Date: 2020-12-02 09:03:25

> That's not what I have in mind. Macros don't solve the problem. What I
> have in mind is that there is a single library that, in its interface,
> can seamlessly take either boost::fs::path or std::fs::path, without
> the user having to define anything.
> Of course, when building the library, you probably would need to have
> Boost.Filesystem available.

This may work for simple types like string_view. But it won't work for
(non-header-only) libraries using e.g. fs::path. At some point you have
to convert to either type or to a third and that is gonna cost you

Additionally that interface may need includes to either or would require
the user to include that first introducing an include-order issue.

And finally once you return a type you have no way for "either" (again
except for simple types that could on-the-fly convert) and that too
requires an explicit choice for the include.

IMO it would be enough on a cost-benefit ratio to go to C++11 by
basically banning the use of MPL in Boost (the single-worst offender on
compile times) and reducing the use of type_traits to the absolute
minimum. Those 2 are (transitively) in the largest chunk of boost
libraries and hence hit hard on compiletimes. Then using the std
smart-pointers wherever possible would further untangle the libraries.
So basically a bottom-up approach to improvement instead of a fork to
whatever is the current greatest and latest. This could even be done
for/by GSoC, interns or similar. And in ~8 years one can check if C++17
would be a good base point.

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