Season from Month

SeasonFromMonth.swift

enum Month: Int, CaseIterable {
    case jan, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec
}

extension Month {
    var season: Season {
        return Season(month: self)
    }
}

enum Season: Int, CaseIterable {
    case winter, spring, summer, autumn
}

extension Season {
    init(month: Month) {
        let seasonIndex = ((month.rawValue + 1 ) / (Month.count / Season.count)) % Season.count
        guard let season = Season(rawValue: seasonIndex) else {
            fatalError("Incorrect implementation of `seasonIndex` (was: \(seasonIndex)) and/or rawValue of 'Season'")
        }
        self = season
    }
}

extension CaseIterable {
    static var count: Int { return Self.allCases.count }
}

for month in Month.allCases {
    print("\(month) is \(month.season)")
}