On Fri, Oct 6, 2023 at 9:58 AM Timur Doumler <cpp_at_[hidden]> wrote:
>
> Thanks Aaron,
>
> > On 6 Oct 2023, at 16:53, Aaron Ballman <aaron_at_[hidden]> wrote:
> > C23 Footnote 186: Standard attributes specified by this document can
> > be parsed but ignored by an implementation without changing the
> > semantics of a correct program; the same is not true for attributes
> > not specified by this document.
>
> Interesting. It seems a bit ambiguous to me what "parsed but ignored" actually means. If we go with the P2935 (attribute-like) syntax for Contracts and you end up having something like this:
>
> [[ assert: x != 0 ]];
>
> Does "parse" mean that you have to actually parse `x != 0` as an expression, since the grammar for contracts says that the thing after the colon is an expression? Or does "when you see `[[`, skip every token until you reach the matching `]]` " also count as "parse"?

It's a footnote, so we're a bit imprecise with the wording of it. But
the intent here is "parse" means "lex and eat tokens until the closing
]], paying attention to balance (, [, and { with ), ], and }". It's
"parsing" because of the balanced tokens and needing to find the
closing ]]. But the goal is for it to be a valid implementation to see
[[, eat balanced tokens until the closing ]], and drop everything on
the floor.

~Aaron

>
> Cheers,
> Timur
>