Open Radar

 
Juan C Montemayor Elosua04-Jun-2014 03:25 PM

Summary:
Curried functions are covered in the Swift iBook, and so I started playing around with them. 

One example from the book, namely `addTwoNumbers(4)(5)` does not compile, since apparently the second argument in the curried function requires a label.

Local parameter names work, but curried functions do not work (read: ignore) external parameter names.

Furthermore, doing something like:

var add4 = addTwoNumbers(4)
add4(10)

doesn't work, since apparently the add4 call requires a label for the parameter, even though in theory it is the first parameter.

Steps to Reproduce:
Install Xcode 6.0 (6A215l)

Open the attached file. There should be one call that works, and three calls that do not work (corresponding to the three points I have laid out)

Here's the code for good measure:

// Playground - noun: a place where people can play

func addTwoNumbers(a: Int)(to b: Int) -> Int {
    return a + b
}

// Works:
addTwoNumbers(4)(b: 4) // Returns 8

// BUG:
// Expected: No errors. First param name should not require param name (from iBook)
// Actual: "Missing argument label 'b' in call"
var add4 = addTwoNumbers(4)
add4(10)

// BUG:
// Expected: No errors, lets us use the external param name
// Actual: "Incorrect argument label in call (have 'to:', expected 'b:')"
addTwoNumbers(4)(to: 6) // Result: 10

// This won't compile, since names are required for any param that's not the first
// This is code from the Swift iBook

// BUG:
// Expected: No errors
// Actual: "Missing argument label 'b' in call"
addTwoNumbers(4)(5) // Returns 9


Expected Results:
There should be no errors when opening the file.

Actual Results:
There are three distinct errors:

- Not able to use external parameter names in curried functions
- Forced to use parameter name even when it is the first parameter in a newly created curried function
- The iBook example `addTwoNumbers(4)(5)` doesn't compile. That may be an issue with the book itself though... (please file radar? :)

Version:
Xcode Version 6.0 (6A215l)
OS X 10.9.3 13D65

Notes:
Thanks for all your work! Xcode and Swift are lookin' fine ;)

Configuration:


Attachments:
'curry_bug.playground.zip' was successfully uploaded.