Grade School

Instructions

Given students' names along with the grade they are in, create a roster for the school.

In the end, you should be able to:

• Add a student's name to the roster for a grade:
  • "Add Jim to grade 2."
  • "OK."
• Get a list of all students enrolled in a grade:
  • "Which students are in grade 2?"
  • "We've only got Jim right now."
• Get a sorted list of all students in all grades. Grades should be sorted as 1, 2, 3, etc., and students within a grade should be sorted alphabetically by name.
  • "Who is enrolled in school right now?"
  • "Let me think. We have Anna, Barb, and Charlie in grade 1, Alex, Peter, and Zoe in grade 2, and Jim in grade 5. So the answer is: Anna, Barb, Charlie, Alex, Peter, Zoe, and Jim."

Note that all our students only have one name (it's a small town, what do you want?), and each student cannot be added more than once to a grade or the roster. If a test attempts to add the same student more than once, your implementation should indicate that this is incorrect.

Implementation

To complete this exercise you need to implement the struct by defining the data type school and implementing the functions:

• newSchool
• add
• roster
• grade

Chapter 3 of Notes on Programming SML/NJ discusses the use of signatures and structs.