What is the difference between `map`, `flatMap`, and `compactMap`?

Answer: All three transform collections but handle the results differently.

Function	Use case
map	Transform each element, keep all results
compactMap	Transform and remove nil results
flatMap	Transform and flatten nested collections

Code Example:

let numbers = [1, 2, 3, 4]

// map — transforms every element
let doubled = numbers.map { $0 * 2 }
// [2, 4, 6, 8]

// compactMap — removes nils
let strings = ["1", "two", "3", "four"]
let integers = strings.compactMap { Int($0) }
// [1, 3]

// flatMap — flattens nested arrays
let nested = [[1, 2], [3, 4], [5, 6]]
let flat = nested.flatMap { $0 }
// [1, 2, 3, 4, 5, 6]