Swift Functional Programming - Second Edition

Functions

Functions are self-contained blocks of code that perform a specific task.

In Swift, functions are first-class citizens, meaning that they can be stored, passed, and returned. Functions can be curried and defined as higher-order functions that take other functions as their arguments.

Functions in Swift can have multiple input parameters and multiple returns using tuples. Let's look at the following example:

func greet(name: String, day: String) ->String {     return "Hello \(name), today is \(day)" } greet(name: "Francois", day:"Saturday") 

Functions can have variadic parameters. Consider the following example:

// Variable number of arguments in functions - Variadic Parameters func sumOf(numbers: Int...) -> (Int, Int) {  var sum = ...