Function returning function and calling a function that takes Variadic parameters using an array in Swift

Question

I am trying to make a curry function like in Lodash http://lodash.com/docs#curry

Unfortunately I am getting two compile errors.

func curry(fun: (Any...)) -> ((Any...) -> (Any)) {
    let count = fun.0.count
    var resultArgs: Any[] = []
    func generator(newArgs: Any...) -> ((Any...) -> (Any))? {
        for (index, elem) in enumerate(newArgs) {
            if resultArgs.count >= count {
                break
            } else {
                resultArgs += elem
            }
        }

        if resultArgs.count >= count {
            // fun(resultArgs)
            // Commenting fun now cause that throws a compile error saying array cannot be passed in Variadic parameter function
            return nil
        } else {
            return generator
        }
    }
    return generator
}

There are two issues here:

Segmentation faults for some reason on the generator function. Idea behind this function is to take parameters and return a new function or not return nothing at all and evaluate the function fun passed in the curry function
Passing array of arguments to a function that accepts Variadic parameters. This should be a given in a language as we can do this using the performSelector in Objective-C

How can I solve these two problems?

I am getting the following error for the generator function which is a segmentation fault during compile time

1.  While emitting IR SIL function @_TTRXFt_oGSaP__oBolGSaP__dSioXFo_oGSaP___oGSqFtGSaP___P____oGSqFtGSaP___P___XFo_oGSaP___oGSqFtGSaP___P___ for 'generator'
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: swift frontend command failed due to signal (use -v to see invocation)
Command /Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift failed with exit code 254

There are lots of bugs in the Swift compiler right now. Using a nested function inside itself like you're doing is one of the things that will crash the compiler. e.g. func foo() { func bar() { bar() } } — newacct
– newacct, Commented Jun 9, 2014 at 18:12

David Lawson · Accepted Answer · 2014-06-08 16:38:15Z

1

This is the closest I got at accepting multiple arguments. It looks like it treats arguments as tuples, according to the error message given for curry2...

func curry<T, U>(fun: (T) -> U) -> (T)->U {
    return fun
}

func curry2(fun: (Any...) -> Any) -> (Any...)->Any {
    return fun
}

func to_curry(a: Int, b: Int) -> Int { return a + b }

func test() {
    curry(to_curry)(3, 5) // returns 8
    curry2(to_curry)(3, 5)
    // tuple types '(Any...)' and '(Int, Int)' have a
    // different number of elements (1 vs. 2)
}

And I can't find any way to count tuples other than doing something like this:

let tuple = (1, 2)
let count = sizeofValue(tuple)/sizeof(Int)

edited Jun 8, 2014 at 16:38

answered Jun 8, 2014 at 16:08

David Lawson

7,9425 gold badges33 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Encore PTL Over a year ago

The solution you have is not a curry function. It only works if you pass both arguments then I would just call the function directly. What I want to do is let add3 = curry(to_curry)(3) and then you can call add3(5) and it will return 8

David Lawson Over a year ago

I just managed to accept a varying number of arguments, didn't get any further than that unfortunately.

Collectives™ on Stack Overflow

Function returning function and calling a function that takes Variadic parameters using an array in Swift

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related