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Swift Functional Programming - Second Edition by Dr. Fatih Nayebi

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The map function

Swift has a built-in higher-order function named map that can be used with collection types such as arrays. The map function solves the problem of transforming the elements of an array using a function. The following example presents two different approaches to transform a set of numbers:

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 { "\($0)$" } 

The first approach to solve the problem is imperative and uses a for-in loop to go through the collection and transform each element in the array. This iteration technique is known as external iteration because ...

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