In other words, since Martin is teaching EECS 492, he must have taken this course earlier.Įxample 4: List all courses that martin has taken?- taken(martin, X), print(X), nl, fail. Note that although taken(martin, eecs492) is not directly stated in the KB, prolog makes the logical inference from the fact that teach(martin, eecs492) and taken(X, Y) :- teach(X, Y). To question the KB if a fact is true, one make a query after ?-.Įxample 1: Is math214 an eecs course?- eecs(math214).Įxample 2: Is math214 a prerequisite of eecs492 ?- prerequisite(math214, eecs492).Įxample 3: Have martin taken eecs492 ?- taken(martin, eecs492). for legal details.įor built-in help, use ?- help(Topic). SWI-Prolog comes with ABSOLUTELY NO WARRANTY.

pl file, open it in the SWI-prolog, you should see something similar to this: Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.22-114-g7e1bb6838) To describe this rule, we could write: taken(X, Y) :- teach(X, Y). The :- should be read as “if”, or “is implied by”.Įxample 1: Use the following predicates to describe the facts: teach(X, Y) => taken(X, Y): If X teaches Y, X must have taken Y. The basic format for a fact is predicate(arguments) :- predicate(arguments). Given that martin has taken eecs445, and teaches eecs280 and eecs492, we could write: prerequisite(eecs280, eecs281). The predicate may take more than 1 argument.Įxample 2: Use the following predicates to describe the facts: prerequisite(X, Y): X is a prerequisite of Y. To describe eecs280, eecs281, eecs445, eecs492 and math214, we could write: eecs(eecs280). The basic format for a fact is predicate(arguments).Įxample 1: Use the following predicates to describe the facts: eecs(X): X is an EECS course. Prolog programming is all about writing knowledge bases (KB), collection of facts and rules.

Block world problem in prolog