On 22.02.2017 17:22, Haravikk via swift-evolution wrote:
On 22 Feb 2017, at 13:19, Derrick Ho <wh1pch...@gmail.com
<mailto:wh1pch...@gmail.com>> wrote:
I've read the pitch, but it isn't clear what the ask is or what benefit
it would give.
The purpose of the feature is to enable selection of identically named
methods with similar signatures. This came up in the protocol-oriented
integers debate on the ability to have arithmetic methods with and without
overflow. Like so:
protocol IntegerArithmetic {
func adding(_ other:Self) -> Self
func adding(_ other:Self, reportingOverflow) -> (Self, Bool)
}
var a = 2, b = 3
let resultWithoutOverflow = a.adding(b)
let resultWithOverflow = a.adding(b, reportingOverflow)
Isn't this very confusing about what 'reportingOverflow' *is*? IMO it looks
like reportingOverflow is a variable/property defined in some place and has
some value. While "a.adding(b, .reportingOverflow)" is obvious about what
.reportingOverflow is, just like separate addingWithReportingOverflow method.
Do I understand correctly, that the proposed solution is some kind of sugar
to not have separate method named like 'addingWithReportingOverflow' ?
In any case IMO such argument label should have special syntax on caller
site.. don't know, probably:
let resultWithOverflow = a.adding(b, :reportingOverflow)
probably with the same declaration:
func adding(_ other:Self, :reportingOverflow) -> (Self, Bool)
if we keep semicolon *after* such trailing label, then we have the problem :
let x = foo(reportingOverflow:)
was foo called with trailing label 'reportingOverflow' or x is assigned to
function foo with one 'real' argument?
Here we have two different methods, one reporting overflow and one without,
using the label to enable selection, rather than having to have an
addingWithOverflow() method or similar.
Currently the alternative is to do something like:
enum ReportingOverflow { case .reportingOverflow }
protocol IntegerArithmetic {
func adding(_ other:Self) -> Self
func adding(_ other:Self, _) -> (Self, Bool)
}
var a = 2, b = 3
let resultWithoutOverflow = a.adding(b)
let resultWithOverflow = a.adding(b, .reportingOverflow)
Basically the ability to use the label for method selection is an
alternative to either defining an enum as above, or having to use a
different method name.
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
