Vladimir,
I don't disagree with you about bitwise operations (please read my email
again). I'm saying when it comes to `??`, we don't have the evidence necessary
for proposing a breaking change.
> On 08 Sep 2016, at 14:21, Vladimir.S <sva...@gmail.com> wrote:
>
> Why do you need to see some precedence (…) while this construction is so
> simple and obviously would be used often and *will* cause bugs. (…)
Let me put it differently: I still haven't seen, nor was I able to conceive
myself, a realistic example where `??` would cause problems.
>> The original motivation by Erica simply failed to compile (…)
>
> Sorry, but you are just not right.
Let me remind you that the original motivation from Erica wasn't about which
way `foundIndex ?? lastIndex + 1` goes but about whether `let y = 5 + x ?? 2`
compiles at all.
> The code compiles without even warning:
>
> let foundIndex : Int? = 1
> let lastIndex = 2
>
> let nextIndex = foundIndex ?? lastIndex + 1
It certainly does compile. But is it realistic? Look at the variable names:
does this code make any sense at all? What is `lastIndex`? What is `lastIndex +
1`? Why not `things.endIndex`? Indeed, why not:
let foundIndex: Int? = things.index(of: something)
let nextIndex = foundIndex.map { $0 + 1 } ?? things.endIndex
That said, I give you the benefit of the doubt – I still believe there can be
examples where `??` may be confusing. But without seeing any such examples from
the real world, I don't think we have a case for changing `??`.
> After I showed the code compiles, would you change your opinion?
No, not with these examples.
* * *
Finally:
> IMO the best solution (…) would be to require (…) parenthesis when operators
> from different groups are mixed in the same expression. IMO no need in
> complex rules to make Swift safer. I.e. when you have a = 10 + 5 * 10 - you
> don't need parenthesis, when you have a = b << 4 - also all is ok, but if
> you have a = b << 4 + 5 * 10 - you'll have a warning until add parenthesis to
> make your intention clear. (…)
Look, changing how `b << 4 + 5 * 10` is compiled is exactly what I was
proposing. With my changes, it would become a compiler error. IMO, it ought to
be parenthesised explicitly as either
(b << 4) + 5 * 10
or
b << (4 + 5 * 10)
depending on which one was intended.
— Pyry
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
