[swift-evolution] [Discussion] Breaking precedence

Xiaodi Wu xiaodi.wu at gmail.com
Mon Aug 1 16:52:50 CDT 2016

On Mon, Aug 1, 2016 at 4:41 PM, Anton Zhilin via swift-evolution <
swift-evolution at swift.org> wrote:

> Disclaimer: I have not (yet) prepared a proposal, or even something that
> could be considered a draft, but I want to hear public opinion on the topic.
> SE-0077 (about precedence groups) has been successfully implemented for
> Swift 3. (A thousand thanks to John McCall!) It suggests a model where we
> can prohibit certain operators from standing next to each other.
> This was intended to be the second part of that proposal. We now have to
> think if we should drop some precedence relationships between standard
> operators. Here are examples of parentheses dropping that can be ambiguous
> to reader:
> 1/3 as Double   // should we prohibit this?

Why should we? I would absolutely want that to work exactly as it does now

1 | 2 ^ 3   // or this?

No. Both of those are bitwise operations. They are often used together.
They have a refined relative precedence in Swift that makes sense.

a && b | c   // or this?

Now that's more interesting. Maybe?

Should we break standard precedence hierarchy and if yes, how?
> For those involved in the mentioned proposal, how exactly should standard
> precedence groups relate?
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