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

Read and understand the following program:

• It's a Tie -- I have provided a sample solution for this one, and a page of notes on how it works. Use this as a model for your own solutions. (The "main" function is solve).

Solve two standard (commercial) logic puzzles.

• Solar Flair
• City Paladins

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:
  • Prolog tries to prove things, so if expression E contains unbound variables, \+E will try to find variable bindings that will make E true.
  • \+ works as you would expect when all variables are completely instantiated (bound).
• While a logic puzzle may be difficult to solve, it is easy to check whether a solution is correct: Just check whether it satisfies each of the numbered rules in the problem.
• If you want to solve logic puzzles manually, here's how to do it. However, that isn't the way to do it by a computer!

Sample puzzle (It's a Tie)

Puzzles for you to solve

Grading

This one will be easy to grade; your program should produce the correct solution. We may deduct points if your style is egregiously bad.

Due date