Exercises part 2

module Tutorial.DataTypes.Exercises2

1. Implement an equality test for Title (you can use the equality operator (==) for comparing two Strings):

   total
   eqTitle : Title -> Title -> Bool
   

2. For Title, implement a simple test to check, whether a custom title is being used:

   total
   isOther : Title -> Bool
   

3. Given our simple Credentials type, there are three ways for authentication to fail:

   • An unknown username was used.
   • The password given does not match the one associated with the username.
   • An invalid key was used.

   Encapsulate these three possibilities in a sum type called LoginError, but make sure not to disclose any confidential information: An invalid username should be stored in the corresponding error value, but an invalid password or key should not.

4. Implement function showError : LoginError -> String, which can be used to display an error message to the user who unsuccessfully tried to login into our web application.