[Swift] Example of filter, map, and reduce

FilterMapReduce.swift

enum Faction {
   case empire
   case rebels
}
 
let characters: [(name: String, faction: Faction, episodes: [Int])] = [
    (name: "Darth Maul", faction: .empire, episodes: [1]),
    (name: "Han Solo", faction: .rebels, episodes: [4, 5, 6]),
    (name: "Palpatine", faction: .empire, episodes: [1, 2, 3, 5, 6]),
    (name: "R2-D2", faction: .rebels, episodes: [1, 2, 3, 4, 5, 6]),
    (name: "Grand Moff Tarkin", faction: .empire, episodes: [6]),
    (name: "Leia Organa", faction: .rebels, episodes: [4, 5, 6]),
    (name: "Luke Skywalker", faction: .rebels, episodes: [4, 5, 6])
]
 
// Who in the list of characters from the rebel faction has appeared
// in the most episodes and how many?
 
// FILTER: Keep the rebels, throw away the imperial characters.
let rebels = characters.filter({ $0.faction == .rebels })
 
// MAP: Transform list of rebels to include the number of appearances
// instead of the list of episodes. Also throw away the faction.
let rebelsWithAppearances: Array<(name: String, appearances: Int)> = rebels.map({
     (name: $0.name, appearances: $0.episodes.count)
})
 
// REDUCE: Reduce the list to only the rebel character with the
// most number of appearances.
let defaultRebel = (name: "Nobody", appearances: 0)
let (name, mostAppearances) = rebelsWithAppearances.reduce(defaultRebel, {
    ($0.appearances > $1.appearances) ? $0 : $1
})
 
print("\(name) is the rebel with most appearances (\(mostAppearances)).")