--The first string is the name and the second is the user ID, just for test
type User = (String, String, Integer)
users = [("Marcelo Castro", "1234", 2),
("Joao Vicente Claudino", "1235", 2),
("Wilson Brandao", "1236", 2),
("Humberto Teixeira", "1237", 2),
("Luiz Gonzaga", "1238", 2),
("Severino Dias", "1239", 2),
("Hermeto Pascoal", "1234", 2)]
checkUser :: User -> [User] -> Bool
checkUser user userList
= if (head (filter (\userParse -> userParse == user) userList)) == user
then True
else False
userRegistration :: User -> [User] -> [User]
userRegistration user list
| checkUser user list = list
| not(checkUser user list) = (user : list)
| otherwise = []