Fundamentals of Computer Science I (CS151.02 2007S)

Project Report: Project 2: Grading

This assignment is also available in PDF.

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


or the form


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,Extra,6,Convo+Convo+CS Extra+Softball+Ultimate+Concert
Rebelsky,Exam2,75,was 25
Rebelsky,Exam4,0,Did not take the final
Rebelsky,Participation,90,docked for talking too much


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:

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:

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:

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

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))))



Monday, 7 May 2007 [Samuel A. Rebelsky]

Tuesday, 8 May 2007 [Samuel A. Rebelsky]


Disclaimer: I usually create these pages on the fly, which means that I rarely proofread them and they may contain bad grammar and incorrect details. It also means that I tend to update them regularly (see the history for more details). Feel free to contact me with any suggestions for changes.

This document was generated by Siteweaver on Tue May 8 11:42:24 2007.
The source to the document was last modified on Tue May 8 11:42:17 2007.
This document may be found at

You may wish to validate this document's HTML ; Valid CSS! ; Creative Commons License

Samuel A. Rebelsky,

Copyright © 2007 Samuel A. Rebelsky. This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License. To view a copy of this license, visit or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA.