Transform a country acronym to an emoji flag

countryFlag.swift

func flag(country: String) -> String {
    let base = 127397 // Root Unicode flags index
    var usv = String.UnicodeScalarView() // Prepare a Unicode string
    for i in country.utf16 { // Loop over the country acronym letters
        let inc = Int(i) // The letter's ASCII index
        let code = UnicodeScalar(base + inc) // Shift the letter index to the flags index
        usv.append(code) // Append the grapheme to the Unicode string
    }
    return String(usv)
}

let flagged = flag("FR") // prints "🇫🇷"