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{ "\($0)$" }