Niall,

on Sun, 31 Jan 2021 17:37:21 +0000 you (Niall Douglas via Liaison
<liaison_at_[hidden]>) wrote:

> Hopefully this made sense to you? Just to be clear, C under this
> proposal

this proposal?

I know that we now have WG14 proposals for integrating lambdas into C
:-)

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2633.pdf
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2634.pdf
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2635.pdf

but I wasn't aware that there is one for this:

> would have most of C++ lambdas, but C's equivalent to
> std::function<ret(args...)> would probably be something like
> _Function(ret, args...). i.e. _Function would be a compiler built-in.

already. I kept these things out for the moment, to ensure
that WG14 first looks into everything that can be made here without
ABI changes or additions.

> I'm not a language person, nor a compiler person, but it seems to me
> that dynamic runtime types do not easily produce bare metal execution
> performance. I think indirection of dynamic information whilst
> keeping the top level of the type system 100% static is a better
> design approach.

If you put this in this generality, it immediately sounds like a big
deal.

VLA (or VM types for that matter) only have the size (or sizes if
multidimensional) as dynamic components and are not very difficult,
neither to implement nor to use. C has them since a long time and they
work well. And, contrary to the common belief and urban legends, they
can be used to make programming with large arrays or even matrices
much safer.

I would hope that we could go here in a similar way to what I am
trying to do with lambdas for WG14: take the simple and
existing things that are well accomplished and mastered in one
language and pull them into the other language to broaden the
intersection. VM types here would be important to have for function
interface compatibility between C and C++.

Thanks
Jens

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