CIS 554 Assignment 1: Logic Puzzles
Fall 2011, David Matuszek

# Purposes of this assignment

• To give you some experience with logic programming.
• To introduce lists in Prolog.
• To emphasize the declarative nature of Prolog. (The entire program consists of a statement of the problem, not some algorithm to solve the problem.)

# General idea of the assignment

Solve two standard (commercial) logic puzzles.

I am providing three such puzzles:

• It's a Tie -- I have provided a sample solution for this one. Use this as a model for your own solutions.
• Imaginary Friends -- The first part of your assignment is to write (and turn in) a Prolog program to solve this logic puzzle. Once you understand the "It's a Tie" solution, this should be easy. Do this one first.
• Star Tricked -- The second part is to write (and turn in) a Prolog program to solve this logic puzzle. This one is a little trickier--you need to figure out how to describe the ordering of weekdays--but it's not too hard..

Notes:

• Use SWI-Prolog for this assignment (and the next).
• Here's an (old) Concise Guide to Prolog which I wrote up. Still accurate, but not very pretty.
• One of my problems in solving these was spelling errors. Prolog checks for singleton variables, but there is no such check for misspelled atoms, such as `spiegel` instead of `speigel`. Be especially careful of this.
• These problems make unusually extensive use of the "not" operator,` \+`. Here's what you need to know about this operator:
• `\+ `works as you would expect when all variables are completely instantiated (bound).
• Prolog tries to prove things, so if expression E contains unbound variables,` \+E` will try to find variable bindings that will make E true.
• It is easy to check whether a solution is correct: Just check whether it satisfied each of the numbered rules in the problem.

Wednesday, September 14, before 6:00am. Please zip up and turn in three files to Blackboard--your two` .pl` files, along with a file containing the two solutions (copy from the output area and paste them into a text file). Note that I require a zip file, not some other form of compressed files.