zalgo.swift

func zalgo(_ string: String, intensity: Int = 5) -> String {
    let combiningDiacriticMarks = 0x0300...0x036f
    let latinAlphabetUppercase = 0x0041...0x005a
    let latinAlphabetLowercase = 0x0061...0x007a
    
    var output: [UnicodeScalar] = []
    for scalar in string.unicodeScalars {
        output.append(scalar)
        guard (latinAlphabetUppercase).contains(numericCast(scalar.value)) ||
              (latinAlphabetLowercase).contains(numericCast(scalar.value))
        else {
            continue
        }
        
        for _ in 0...(Int.random(in: 1...intensity)) {
            let randomScalarValue = Int.random(in: combiningDiacriticMarks)
            output.append(Unicode.Scalar(randomScalarValue)!)
        }
    }
    
    return String(String.UnicodeScalarView(output))
}

You're right, @MatthiasLamoureux — I'm not sure why I was using those ranges here. Thanks for pointing this out.