[swift-evolution] Nil coalescing operator precedence

[Антон Жилин]

Nice points, I also think that unless operators are from the same domain,
more parentheses is better.
Other than that, what rules do we need? I can name these:
1. Assignment operators have lower precedence than most operators
2. Arithmetics has higher precedence than comparative and logical
operators. I don't think that ?? belongs to arithmetics, it's more like
control flow.
3. Unary operators obviously have higher precedence than everything

> I didn't read se-0077 in details, so have no opinion. Probably you can
describe main ideas of it here in two words.
Replace numeric precedence with precedence relationships between pairs of
operators. If precedence between two operators is undefined, we cannot omit
parentheses.

My thought was basically: "parentheses between some operators must be
enforced by the language" <=> "SE-0077 is needed"

- Anton

2016-06-15 17:17 GMT+03:00 Vladimir.S <svabox at gmail.com>:

>
> On 15.06.2016 16:43, Антон Жилин via swift-evolution wrote:
>
>> `b + c * d / e` is not, obviously.
>>
>
> obviously, for math operators it seems like we don't need any
> clarifications
>
> `a ? b : c + x + y` -- I'd also say not, because, well, it's ternary
>> operator, the special case that everyone should know (otherwise it looks
>> like a mess with ? and : operators).
>>
>
> Yes, it's ternary operator.  But is it
> a ? b : (c + x + y)
> or
> (a ? b : c) + x + y
>
> IMO ambiguous.
>
> `a ?? x + y + z` -- maybe. If not for analogies with || and && and knowing
>> about @autoclosure, I'd say that priority of ?? should be very high.
>>
>>
> The same, is it
> a ?? (x + y + z)
> or
> (a ?? x) + y + z
>
> ? I.e. I'm not asking, just show that the question is not if we know what
> does ?? mean, but how all the expression will be treated.
>
> IMO it's totally false assumption that most of developers(and poor
> beginners) do remember the the correct precedence in such expressions and
> in most cases will not make a bug and so we should not require the
> parentheses. Imagine how each such expression will be crystal clear about
> the order of processing in *any* Swift source code you could find anywhere.
> IMO this will be great advantage of the language.
>
> Now that I think about it, if job of SE-0077 could be done with a linter,
>> then... do we still need it?
>>
>
> I didn't read se-0077 in details, so have no opinion. Probably you can
> describe main ideas of it here in two words.
>
>
>> - Anton
>>
>> 2016-06-15 16:00 GMT+03:00 Vladimir.S <svabox at gmail.com
>> <mailto:svabox at gmail.com>>:
>>
>>     As I understand, the question is if
>>
>>     `a ?? x + y + z`
>>     and
>>     `a ? b : c + x + y`
>>     (or `b + c * d / e`)
>>
>>     an "ambiguous case" ?
>>
>>
>>     On 15.06.2016 15:42, Антон Жилин via swift-evolution wrote:
>>
>>         It's tempting to mention SE-0077 in this context. If it's
>> accepted,
>>         we will
>>         be able to make omission of parentheses an error in ambiguous
>> cases.
>>
>>         - Anton
>>
>>
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