[swift-evolution] [Pitch] UnsafePointer.advanced(to:)

Dave Abrahams dabrahams at apple.com
Tue Jun 6 14:56:48 CDT 2017

on Tue Jun 06 2017, Brent Royal-Gordon <swift-evolution at swift.org> wrote:

>> On Jun 6, 2017, at 9:06 AM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>> Why would this be an extension on UnsafePointer and not KeyPath?
> 1. I can't come up with a name as good as `advanced(to:)` that would
> be attached to the key path. I use `advance(_:)` in the other two
> reasons below, but I don't think it's nearly as clear about what it's
> doing to the pointer.
> 2. Passing the pointer as the parameter would encourage use of `&`, which would be invalid.
> 	(\CGRect.origin.y).advance(&myRect)		// Pointer might be to a temporary
> 	(&myRect).advanced(to: \.origin.y) // Rejected during compilation because & is not allowed
> there
> 3. Passing the key path as a parameter improves the code's appearance when you specify the key path
> in the expression.
> 	myRectPtr.advanced(to: \.origin.y)
> 	(\CGRect.origin.y).advance(myRectPtr) // Requires explicit type name and extra parentheses

IIUC this has nothing to do with "advancing", though.  Maybe "applying"
or even "map" would be a better name?


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