[swift-evolution] Passing functions with default parameters

Oskar Ek oskarek24 at gmail.com
Sat Jun 17 19:14:46 CDT 2017

Hello Swift evolution community!

Developing in Swift, I have many times found myself being frustrated that a function with default parameters can’t be passed to another function.

For example:

// sorts a string alphabetically
func sort(string: String, descending: Bool = false) -> String {
  return String(string.sorted { descending ? $1 < $0 : $0 < $1 })

let strings = [”swift", ”apple”, ”ios”]

If I wanted to map over the strings and sort each one, I would expect this to work:

strings.map(sort(string:)) // expected output: [”fistw", ”aelpp”, ”ios”]

However, this produces the error: use of unresolved identifier 'sort(string:)’

Instead, I have to write:

strings.map { sort(string: $0) }

Anybody else that would appreciate this possibility?
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