String+Extension.swift

import Foundation

extension UnicodeScalar {
    /// `a-z{
    var isLowerCase: Bool {
        return value >= 0x61 && value <= 0x7a
    }
    
    /// @A-Z[
    var isUpperCase: Bool {
        return value >= 0x41 && value <= 0x5a
    }
    
    func uppercased() -> UnicodeScalar {
        if isLowerCase {
            return UnicodeScalar(value - 0x20)!
        } else {
            return self
        }
    }
    
    func lowercased() -> UnicodeScalar {
        if isUpperCase {
            return UnicodeScalar(value + 0x20)!
        } else {
            return self
        }
    }
}