Course roster management in scheme
• Data to be managed
– A class roster is list of student entries of the form
(ID, name, grade)
– Example
(“001”, “John Smith”, 59)
(“010”, “Amy M. Sosa”, 100)
(“500”, “Mike Harris”, 80)
• In scheme, this data structure will be represented as a
list:
((“001” “John Smith” 59) (“010” “Amy M. Sosa” 100) (“500” “Mike Harris” 80))
Course roster management in scheme
• The roster management system supports the
following functions (in the menu):
0. Reset roster
1. Load roster from file
2. Store roster to file
3. Display roster sorted by ID
4. Display roster sorted by name
5. Display roster sorted by grade
6. Display student info
7. Add a student to roster
8. Remove a student from roster
9. Exit
How to maintain the roster?
• There is no storage (variables) in scheme
– The roster has either to be an argument to a
function or a return value.
– The function to print a menu needs to have an
argument for the roster.
• Menu (roster)
Menu system
• Display the menu
• Read input from user
• Perform some operation on the roster and
continue.
• How to do this in scheme? See t1.scm.
Dealing with input
• Read 2 items (id and grade) and return the list
of just two items just read?
(define read-2-items
(lambda ()
(begin
(display “input id and grade: “)
(list (read) (read))
)
)
Let us say if we want to append this item into the roster list, what to do? See t2.scm
Load from file and store to file
• Straight-forward
– (write object file) to write the whole roster to a
file.
– (read file) to read the whole roster from a file.
Sorting
• A function (insert item sorted_list)
– How?
• (Insertionsort l)
– (insert (car l) (insertionsort (cdr l))
Order of software development
• Do NOT write the whole
program in one shot!!!!
– One function at a time. Test
before considering the next
function.