CS 331 Spring 2025  >  Assignment 7 (Coding in Scheme & Prolog)

---

CS 331 Spring 2025
Assignment 7 (Coding in Scheme & Prolog)

Assignment 7 is due at 5 pm Thursday, April 24. (Note that, as per the syllabus, this assignment will not be accepted after the beginning of the final exam period: 1 pm Friday, May 2.) The assignment is worth 70 points.

Procedures

This assignment is to be done individually.

Turn in answers to the exercises below on the UA Canvas site, under Assignment 7 for this class.

• Your answers must consist of the answer to Exercise A (submitted as an attached text/PDF file), the source code for Exercise B (file alternatingSums.scm), and the source code for Exercise C (file collcount.pl).
• I may not look at your homework submission immediately. If you have questions, e-mail me.

Exercises (A–C, 70 pts total)

There will be no test programs posted for this assignment. Test your code!

Exercise A — Running a Fulmar Program

Purpose

In this exercise you will demonstrate that you can execute Fulmar code.

Instructions

Get the file check_fulmar.fmar from the class Git repository. This is a Fulmar source file for a complete program. When it is executed, this program prints “Secret message #5:”. Below that, it prints a secret message. Run the program. What is the secret message?

To execute the program, run fulmar.lua, with the following files in the same directory: check_fulmar.fmar, from the Git repository, and lexit.lua, parseit.lua, and interpit.lua, from previous assignments. At the prompt, type:

:r check_fulmar.fmar

Exercise B — Programming in Scheme

Purpose

In this exercise, you will write a Scheme procedure.

Instructions

Write a Scheme source file alternatingsums.scm as follows. Be sure to follow the Coding Standards.

• Your file must begin with the line “#lang scheme”.
• Your file must define procedure alternatingSums.
  • This takes an arbitrary number of arguments, which will be numbers. It returns a list of length 2 holding the sum of the even-index numbers and the sum of the odd-index numbers. Indices are considered to begin at zero. For example evaluating (alternatingSums 1 20 3 40 5) returns (9 60), because \(1+3+5 = 9\), and \(20+40 = 60\). And (alternatingSums) returns (0 0).
  • Your code does not need to do any type checking or other error checking.
  • Here is a sample DrRacket session using alternatingSums. (File alternatingsums.scm has already have been opened and run.)

    [Interactive Scheme]

    > (alternatingSums 1 2 3 4)
    (4 6)
    > (alternatingSums)
    (0 0)
    > (alternatingSums 56)
    (56 0)
    > (alternatingSums 10 20 30 40 50)
    (90 60)
    > (alternatingSums (* 2 2) (* 3 3) 1)
    (5 9)
    

• Your file may define any other procedures, macros, or variables you wish.

Exercise C — Programming in Prolog

Purpose

In this exercise, you will write a Prolog predicate.

Instructions

Write a Prolog source file collcount.pl as follows. Be sure to follow the Coding Standards.

• Your file defines the predicate collcount/2; that is, collcount is a predicate that takes 2 arguments.
  • Predicate collcount takes arguments as follows: collcount(+n, ?c); that is, the first argument is an input, while the second is either an input or an output.
  • The idea is that n is a positive integer, and c is the number of iterations of the Collatz function required to take n to 1.
  • Your code does not need to do any type checking or other error checking.
  • Here is a sample SWI-Prolog session using collcount.

    [Interactive Prolog]

    ?- [collcount].
    true.
    
    ?- collcount(1, 0).
    true.
    
    ?- collcount(1, C).
    C = 0.
    
    ?- collcount(27, C).
    C = 111.
    
    ?- collcount(27, 200).
    false.
    

• Your file may define any other predicates you wish.
• You may find the following helpful. Prolog has a numerical function mod than computes the integer division remainder, just like the “%” operator in C++. For example:

  [Interactive Prolog]

  ?- K is mod(15, 4).
  K = 3.