Lecture 25 - November 20, 2007

Quiz

Prolog:

To get into the interpreter: pdprolog <return>

To get out of the interpreter: exitsys.

All Prolog statements end with a period. Don't forget to type it.

In LISP we had atoms and lists.

In Prolog we have facts and rules.

In LISP we used the load statement to get code into the LISP interpreter

In Prolog we use consult('filename.pro'). to load a program in

To UNLOAD use forget('filename.pro').

Comments are inserted between /* and */

A Prolog program consists of a database of facts and rules.

We can see all of the predicates in the database by typing dir p.

We can see all of the constants by typing dir.

We can see everything that has been typed in using listing.

Constants begin with lower case letters.

Variables begin with upper case letters.

FACTS are headless Horn clauses.

FACTS can have one or many arguments.

Examples:

tall(troy).

father(sam,joe).

RULES are headed Horn clauses.

RULES have an if in them.

The if is a colon hyphen pair without a space between them.

An and is a comma

Examples:

happy(mary) :- tall(mary).

happy(sam) :- tall(sam), rich(sam).

Facts and rules can be added interactively using asserta and assertz

The problem with using asserta and assertz is that there's no command to save the contents of your data base to disk.

Examples:

asserta(likes(john,mary)).

assertz(likes(john,paula)).

Once you have facts and rules in the database, you can query the database.

Two sets of slides to review

Slides reviewed in class

Slides from text

RESOLUTION and INSTANTIATION are important ideas.

Family.pro as a text file gives us that each person is their own sibling

Family2.pro as a text file eliminates the error

Test.pro as a text file was gone over in 2pm section.