COP 4020 — Programming Languages 1 April 5, 2009
Homework 6: Relational Programming
(aka Logic Programming)
See Webcourses and the syllabus for due dates.
In this homework you will learn a bit about the relational model and basic techniques of logic programming. The
programming techniques include specification of relationships and using generate and test [Concepts] [UseModels].
A few problems also make comparisons with the other models we have studied, and also with embeddings of the
relational model in other languages [EvaluateModels] [MapToLanguages].
Your code should be written in the relational model of chapter 9 of our textbook [RH04]. Thus you should not use
cells and assignment in your Oz solutions. Furthermore, note that the relational model does not include the primitive
IsDet or the library function IsFree; thus you are also prohibited from using either of these functions in your
solutions.
You should use helping functions whenever you find that useful. Unless we specifically say how you are to solve a
problem, feel free to use any functions from the Oz library (base environment), especially functions like Map and
FoldR.
For all Oz programing tasks, you must run your code using the Mozart/Oz system. For these you must also provide
evidence that your program is correct (for example, test cases). Oz code with tests for various problems is available in
a zip file, which you can download from the course resources web page or from problem 1’s assignment on
Webcourses. If the tests don’t pass, please try to say why they don’t pass, as this enhances communication and makes
commenting on the code easier and more specific to your problem.
Turn in (on Webcourses) your code and, if necessary, output of your testing for all questions that require code. Please
upload text files with your code that have the suffix .oz and text files with suffix .txt that contain the output of your
testing. Please use the name of the main function as the name of the file. (In any case, don’t put any spaces in your
file names!)
Your code should compile with Oz, if it doesn’t you probably should keep working on it. If you don’t have time, at
least tell us that you didn’t get it to compile.
If we provide tests and your code passes all of them, you can just indicate with a comment in the code that your code
passes all the tests. Otherwise it is necessary for you to provide us test code and/or test output. If the code does not
pass some tests, indicate in your code with a comment what tests did not pass, and try to say why, as this enhances
communication and makes commenting on the code easier and more specific to your problem than just leaving the
buggy code without comments.
Don’t hesitate to contact the staff if you are stuck at some point.
Read Chapter 9 of the textbook [RH04]. (See the syllabus for optional readings.)
Reading Problems
The problems in this section are intended to get you to read the textbook, ideally in advance of class meetings.
Read chapter 9’s introduction in the textbook [RH04] and answer the following questions.
1. (5 points) [EvaluateModels]
Could the relational model be used to implement a data abstraction, Box as in the previous homework, which acts
like a cell? Briefly explain.
Read chapter 9 through section 9.1 in the textbook [RH04] and answer the following questions.
2. (5 points) [MapToLanguages]
