Points.swift

import Foundation

typealias Points = Int

extension Points {
    func rank() -> Rank {
        return Rank(self)
    }
}

enum Rank {
    case Recruit, Rookie, Pro
    
    init(_ points: Points) {
        switch points {
        case 0..<100:
            self = .Recruit
        case 100..<200:
            self = .Rookie
        default:
            self = .Pro
        }
    }
}

// demo
let rank = 10.rank()