Directions for using PDProlog

written by Dr. Elizabeth Adams

Use any editor you want to create your Prolog database. I have two databases in this directory.

Make sure that your file has the extension .pro

To get into PDProlog, click on PDProlog.exe or in DOS type PDProlog <cr>

To get out of PDProlog type exitsys.<cr> at the prompt

To load a file, which is easier if you have it in the same directory as your PDProlog.exe,

type consult filename.<cr> where filename is the name of the file For example: consult family.<cr>

alternatively you can type consult (‘filename.pro’). – using single quotes. You can use a path if the database you wish to consult isn’t in the same directory.

To see what was loaded or what is currently in the database type listing.<cr>

To see what the predicates in the database are and how many of each there are type dir p.<cr>

To add a fact or rule to your database type either asserta or assertz followed by the fact or rule. asserta adds what you type to the front of the database. assertz adds what you type to the end of the database. Here's an example : assertz (female(mary)).<cr> will add the predicate female(mary). to the end of the database. Neither adds anything to the file that you loaded. Nothing that you typed in using asserta or assertz will still be there when you exit pdprolog and come back.

If you want to ask a question (i.e. pose a query), just type it in. For example, to see who the women in the family data base are, just type: female(Who).<cr> Upper case letters in the argument list are variables. Lower case are constants.

If you look at the predicate (fact) mother (martha, astrid), you have no way of knowing who is the mother and who is the daughter so you don't know whether to pose the query

mother(Mother, Daughter).<cr> or mother (Daughter, Mother).<cr>

There is nothing in the language which tells you which is correct. Sometimes, it is possible to tell if one of the names is male but the best thing to do when you are constructing a database is to put in a comment showing which is appropriate. In PDProlog, comments are enclosed in /* */

An appropriate comment would be /* mother (mother child) */

You can keep a record of your work by using the built-in predicate tell. The problem with using

tell is that it is a total re-direct to disk and you don't see what is happening while it is occurring.

If you want to try it type tell 'drivename:\path\filename.out'. <cr> You need the single quotes if you are not using a filename in the current directory (i.e. if you need to specify drive and path).

When you are done working type told.<cr> before you type exitsys.