Brent Yorgey wrote
Someone did respond to your question, with a link to the data-accessor package on Hackage (you could also take a look at fclabels or lenses). Do those help address your issue?
It's not accessing the data that concerns me, it's updating other elements. Imagine a system that tracks student registration. data Student = Student { sName :: String {- , ... Other stuff -} , coursesTaking :: [Course] } * data Rank = Assist | Assoc | Full data Instructor = Student { iName :: String , rank :: Rank -- defined, say, as data Rank = Assist | Assoc | Full {- , ... Other stuff -} , coursesTeaching :: [Course] } data Course = Course { cName :: String , units :: Int {- , ... Other stuff -} , instructor :: Instructor , enrolledStudents :: [Student] } Suppose I want a function that drops a student from a class. drop :: (Course, Student) -> (Course, Student) I'm declaring the function as pair to pair because both change. If I run drop, I get a new Course record and a new Student record. Doesn't that mean I have to change all the Student, Instructor, and Course record s that refer to them, which also means I have to change all the Course record s that refer to them, etc.? Wouldn't I have to write something like this? data DataBase = DB { students :: [Student] , instructors :: [Instructor] , courses :: [Course] } drop :: DB -> Course -> Student -> DB But even if I do that, doesn't that require a lot of code to get everything updated? Is there a simple way to write that function? In a previous message I guessed that the best way to do it is with Maps, e.g. Map Student [Course] etc. I'd very much appreciate seeing the recommended code for the drop function. Thanks. * *-- Russ* P.S. I'll admit that I've spent virtually no time with monads and would prefer to avoid them if possible.