     }
 }
 
+// MARK: - Convenience Extension
+
 extension String {
     public func validate(rule: ValidationRule<String>) -> Bool {
         return rule.validate(self)

// MARK: - Built-in Rules

extension ValidationRule where Input == String {
    public static var email: ValidationRule {
        return "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}"
    }

    /// Individual Taxpayer Identification Number.

            transform: { $0.replace("-", with: "") }
        )
    }
}
