> On Oct 24, 2016, at 10:15 PM, Chris Lattner <[email protected]> wrote:
>
>>
>> On Oct 24, 2016, at 9:40 AM, Joe Groff via swift-evolution
>> <[email protected]> wrote:
>>
>>
>>> On Oct 22, 2016, at 5:53 PM, Jonathan S. Shapiro
>>> <[email protected]> wrote:
>>>
>>> I missed this earlier posting from Joe Groff, who wrote:
>>>
>>> In the discussion about operators, I wonder whether it makes sense to
>>> formally separate "identifier" and "operator" characters at all. ...
>>>
>>> The consequence if we do not formally separate the operators (verbs) from
>>> the identifiers (nouns) is that white space will be needed around all
>>> operators. That's not necessarily a bad thing, but it would be a
>>> significant and incompatible departure from today's Swift, both in terms of
>>> actual source code breakage and in terms of the "look and feel" that many
>>> people feel passionate about.
>>
>> That's not a strict requirement. If we require operator usage to be declared
>> explicitly, the lexer can accommodate those declarations. Since operators
>> only appear as part of expressions inside bodies, the operator import or
>> declaration doesn't even necessarily have to be ordered at the top of the
>> file since we can still skip function bodies when parsing declarations
>> (though I think we'd want to encourage imports on top anyway for the benefit
>> of readers). This wouldn't be unprecedented—operators as they stand already
>> effectively require an extra pass of parsing.
>
> Ok, but to clarify the requirement, *every* file would have to declare the
> operators it is using at the top of the file. It isn’t enough for them to be
> declared in some file within the current module. Not having this property
> breaks the ability to do a quick parse of a file without doing name lookup.
Yeah, that's a tradeoff. I think that requiring non-standard operator use to be
explicitly declared could be a good thing, though, since I don't think that we
can realistically expect users to learn or intuitively agree on what glyphs are
"operator" or "identifier", no matter what character set we design.
> In addition to the tooling impact, going with such an approach would be very
> inconsistent with the rest of Swift’s grammar, which aims to be order
> independent (except in script files / top level code).
As long as { } aren't in the operator character set, we should still be able to
skip function bodies without parsing, so operator use declarations could still
be order-independent at the top level of declarations. (Whether it's a good
idea to bury your import declarations in the middle of your other decls is
another story.)
-Joe
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