Function currying

Function currying translates a single function with multiple arguments into a series of functions each with one argument. Let's examine an example.

Suppose that we have a function that combines firstName and lastName to return the full name as follows:

func extractFullName(firstName: String, lastName: String) -> String { 
    return "\(firstName) \(lastName)" 
} 

This function could be translated into a curried function as follows:

func curriedExtractFullName(firstName: String)(lastName: String) -> String { 
    return "\(firstName) \(lastName)" 
} 

As seen from this example, we replace the comma with ) ( parentheses. So now we can use this function as follows:

let fnIncludingFirstName = curriedExtractFullName("John") 
let extractedFullName = fnIncludingFirstName(lastName: "Doe") 

Here, fnIncludingFirstName will already have firstName in it so that, when we use it, we can provide lastName and extract the full name.

Starting with Swift 2.2, Apple deprecated function currying...