On 3. Aug 2023, at 23:47, Tim Bray <tbray@xxxxxxxxxxxxxx> wrote:
>
> I really do think that in RFCs, when there’s something that’s optional, it’s really better to say why it’s optional and what might motivate choosing one option or another.
But they are not “optional".
They aren’t there:
filter-selector = "?" S logical-expr
You can use other features of the language to put some there, if you really want to:
logical-expr = logical-or-expr
logical-or-expr = logical-and-expr ...
logical-and-expr = basic-expr ...
basic-expr = paren-expr / ...
paren-expr = [logical-not-op S] "(" S logical-expr S ")"
; parenthesized expression
You could use ?!(!(foo)) as well, and I also wouldn’t say that !(!(…)) is “optional”.
(I wouldn’t mind adding a note explaining why the parentheses are in the examples where they are.
But I don’t know why we put them there.)
Grüße, Carsten
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