Re: [iostreams] When plan to move to C++20

From: Jeff Garland (azswdude_at_[hidden])
Date: 2023-02-17 16:01:44

On Fri, Feb 10, 2023 at 12:03 PM Seyyed Soroosh Hosseinalipour via
Boost-users <boost-users_at_[hidden]> wrote:

> Thanks for reply, but many of the libraries exist in boost, after some
> years candidate for adding to C++ ISO, so I think if we migrate iostream to
> latest standard of C++, we can candidate this library for ISO, because this
> library is very helpful, and general as standard wants.
>
>
I think it would be perfectly reasonable to update the library for C++20 --
it can be done in a way (aka version macros) backward compatible with older
c++ libraries.

That said, I don't think this design is where the standard is headed in
2023.  Additions to I/O in c++20/23 have largely focused on format and
print from fmtlib. And for good reasons - performance, flexibility, lack of
ABI issues under many evolution scenarios, and unicode support. As simple
example, in c++23 you can say:

  vector<int> v = { 1, 2, 3};
  print( "{}", v ); //[1, 2, 3]
  map<string, int> m = { {"foo", 1}, { "bar", 2 }};
  print( "{}", m ); //{ "bar": 2, "foo", 1}

https://godbolt.org/z/ex4Kerqeq

This is stuff that is fundamental and goes away from the traditional
streams model.  Note print does work files and streams as well, but it
isn't required to.  Many of the filtering cases are now covered by
facilities like ranges::views::filter.  So I'm not sure there's much
appetite for going this direction.

Jeff