Project Report: Project 2: Grading

This project is intended to serve as a form of makeup for the those who are not satisfied with their grade on the first project. It is due on Friday, 18 May 2007.

Summary: In this assignment, you will build a simple grading system.

Background: Representing Grades

Professor R has recorded the grades for the semester in a file, using the following free form format. Each line of the file represents one grade, and either has the form

name,thing,grade

or the form

name,thing,grade,comment

Things are either homework (the word HW plus a number), exams (the word Exam plus a number), a project grade (the word Project), a participation grade (the word Participation), or a count of extra credit (the word Extra).

Exam grades are integers. Homework grades may be Zero, Minus, Check Minus, Check, Check Plus, or Plus. Participation grades are integers. Project grades may be A, A-, B+, B, B-, C+, C, D, F, or Zero. Counts of extra credit are integers.

For example, here are some grades

Davis,Exam1,100
Davis,Exam2,105
Davis,Exam3,104
Davis,Exam4,80
Davis,Extra,6,Convo+Convo+CS Extra+Softball+Ultimate+Concert
Davis,HW1,Plus
Davis,HW4,Plus
Davis,Participation,95
Davis,Project,B
Rebelsky,Exam1,104
Rebelsky,Exam2,75,was 25
Rebelsky,Exam3,85
Rebelsky,Exam4,0,Did not take the final
Rebelsky,Extra,0
Rebelsky,HW1,Check
Rebelsky,HW4,Zero
Rebelsky,Participation,90,docked for talking too much
Rebelsky,Project,A-

Assignment

a. Looking at this problem, it is clear that one thing we'll need to do is to break apart the lines of the file into their component parts. Write a procedure, (split-line line), that, given a string, builds a list of the parts of the string, splitting the string at commas.

> (split-line "Rebelsky,Project,A-")
("Rebelsky" "Project" "A-")
> (split-line "Davis,Extra,6,Convo+Convo+CS Extra+Softball+Ultimate+Concert")
("Davis" "Extra" "6" "Convo+Convo+CS Extra+Softball+Ultimate+Concert")

Note that you can scan through the string using string-ref to find the positions of commas and then use substring to extract portions of the string.

b. We'll assume that we're just trying to compute the grades for a single student. Write a procedure, (gather-grades name filename), that finds all the grades for the named student and builds a five-element vector:

• Element 0 is a list of all the student's exam grades.
• Element 1 is a list of all the student's homework grades.
• Element 2 is the student's project grade.
• Element 3 is the student's participation grade.
• Element 4 is the count of extra credit.

Using the sample grades above, we should get something similar to the following results.

> (gather-grades "Rebelsky" "sample-grades")
#5(("104" "75" "85", "0") ("Check" "Zero") "A-" "90" "0")
> (gather-grades "Davis" "sample-grades")
#5(("100" "105" "104" "80") ("Plus" "Plus") "B" "95" "6")

c. In order to compute numeric grades, we will need to convert the other forms of grades to numbers. Write a procedure, (checkgrade->number grade), that converts a grade on the check/plus/minus scale to a number using the following polices:

• a Plus is worth 110 points,
• a Check Plus is worth 100 points,
• a Check is worth 85 points,
• a Check Minus is worth 75 points,
• a Minus is worth 65 points, and
• and a Zero is worth 0 points.

d. Of course, I use letter grades in addition to the check/plus/minus scale, so we'll need to handle that, too. Write a procedure, (lettergrade->number grade), that converts a grade on the standard letter scale to a number using the following policies:

• an A is worth 95 points,
• an A- is worth 91 points,
• a B+ is worth 88 points,
• a B is worth 85 points,
• a B- is worth 81 points,
• a C+ is worth 78 points,
• a C is worth 75 points,
• a D is worth 65 points,
• an F is worth 50 points, and
• a Zero is worth 0 points.

e. Write a procedure, (samr-policy grade-vector), that computes a numeric grade using the following policies:

• Exams are 45% of the final grade. The lowest exam grade is dropped.
• Homework is 15% of the final grade. The lowest homework grade is dropped. The following rules determine conversion to numeric scores.
• The projet is 15% of the final grade. The following rules determine conversion to numeric scores
• Participation is worth 15% of the final grade.
• The best of the above is worth 10% of the final grade.
• Each unit of extra credit is worth 1/2 point.

In the end, it should be possible to find someone's grade as follows:

(define grade
  (lambda (name file)
    (samr-policy (gather-grades name file))))