Swift Functional Programming - Second Edition

The map function

The map function is a higher-order function that solves the problem of transforming the elements of an array using a function. Consider the following example:

let numbers = [10, 30, 91, 50, 100, 39, 74] var formattedNumbers: [String] = [] for number in numbers {     let formattedNumber = "\(number)$"     formattedNumbers.append(formattedNumber) } let mappedNumbers = numbers.map{ "\($0)$" }