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map and CompactMap and flatMap

on 
 let scores = ["1", "2", "three", "four", "5"]
let mapped: [Int?] = scores.map { str in Int(str) }
// [1, 2, nil, nil, 5] - Two nil values as "three" and "four" are strings.

let compactMapped: [Int] = scores.compactMap { str in Int(str) }
// [1, 2, 5] - The nil values for "three" and "four" are filtered out.

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