Open Radar

 
This is a duplicate of rdar://17284891

Summary:
Suppose you have a variadic function:

    func sum(x: Int…) …

And you have a matching array in your code:

    let vars = [1, 2, 3]

Swift should have a mechanism to pass the array to the function by unpacking the array into the argument list.

Steps to Reproduce:

1. Write a variadic method, e.g.:

    func sum(xs: Int…) -> Int { return reduce(xs, 0) { sum, num in sum + num } }

2. Declare a variable containing an Array with a matching type, e.g.:

    let vars = [1, 2, 3]

3. Try to call the function with the array, using some appropriate syntax, e.g.:

    sum(vars)
    sum(*vars)
    sum(vars…)

Expected Results:
There is some way to do this.

Actual Results:
There is no way to do this.

Notes:
The current best suggestion is to provide another version of the function that accepts an array:

    func sum(vars: Int[]) -> Int { return reduce(xs, 0) { sum, num in sum + num } }
    func sum(vars: Int…) { return sum(vars) }

This does work, but it’s kind of clunky.

The * syntax is based on Ruby and Perl 6. The … is my own suggestion, meant to match the … in a variadic signature. However, I actually think … might be better for indicating currying; I’ll file that bug eventually.