um... how can I cast functions taking one argument to a "generic function
pointer" type?
typealias OneArgsFunction = (Any)->Any
func intToInt(_ i: Int) -> Int { return 4 }
func floatToFloat(_ f: Float) -> Float { return 0.4 }
var function : OneArgsFunction = intToInt
function = floatToFloat
error: f.playground:4:34: error: cannot convert value of type '(Int) -> Int' to
specified type 'OneArgsFunction' (aka '(Any) -> Any')
var function : OneArgsFunction = intToInt
^~~~~~~~
error: f.playground:5:12: error: cannot assign value of type '(Float) -> Float'
to type 'OneArgsFunction' (aka '(Any) -> Any')
function = floatToFloat
^~~~~~~~~~~~
--
C. Keith Ray
Senior Software Engineer / Trainer / Agile Coach
* http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf
> On Nov 3, 2017, at 2:24 PM, Slava Pestov <spes...@apple.com> wrote:
>
> Unfortunately we don’t have a way to invoke a function with a runtime
> argument list because that would require runtime code generation in the most
> general case.
>
> I would hack around it by handling the common cases of no arguments, 1
> argument, 2 arguments, etc up to some fixed number of arguments that you
> consider “enough”. Use a switch on the type of the function.
>
> Slava
>
>> On Nov 3, 2017, at 2:21 PM, C. Keith Ray via swift-users
>> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
>>
>> In the code below, I'm trying to store a reference to a function with any
>> number of arguments, with any return type. And I want to be able to invoke
>> it.
>>
>> Help?
>>
>> See the comments with "*******"
>>
>> typealias Void = ()
>>
>> func equalTypes(_ me: [Any.Type], _ other: [Any.Type]) -> Bool {
>> guard me.count == other.count else { return false }
>>
>> for i in 0 ..< me.count {
>> if me[i] != other[i] { return false }
>> }
>> return true
>> }
>>
>> struct Function {
>> var returnType: Any.Type
>> var argTypes: [Any.Type]
>> var function: Any // ******* any function *******
>>
>> func perform(_ args: [Any]) -> Any {
>> // ******* call function() with args, return result *******
>> return 0
>> }
>>
>> func isCompatible(_ other: Function) -> Bool {
>> return self.returnType == other.returnType &&
>> equalTypes(argTypes, other.argTypes)
>> }
>> }
>>
>> func vToV() {
>> print("vToV")
>> }
>>
>> func intToInt(_ i: Int) -> Int {
>> print("intToInt")
>> return 4
>> }
>>
>> let f = Function(returnType: Void.self,
>> argTypes: [],
>> function: vToV)
>> let r = f.perform([])
>> print(r)
>>
>> let f2 = Function(returnType: Int.self,
>> argTypes: [Int.self],
>> function: intToInt)
>> let r2 = f2.perform([12])
>> print(r2)
>>
>> assert(f.isCompatible(f))
>> assert(!f.isCompatible(f2))
>>
>>
>> --
>> C. Keith Ray
>> Senior Software Engineer / Trainer / Agile Coach
>> * http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf
>> <http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf>
>>
>>
>>
>> _______________________________________________
>> swift-users mailing list
>> swift-users@swift.org <mailto:swift-users@swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-users
>
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