[ovid@tomis data]$ aiprolog spider.pro
Welcome to AI::Prolog v 0.5


?- % no more

?- start.

Enter commands using standard Prolog syntax.
Available commands are:
start.                   -- to start the game.
n.  s.  e.  w.  u.  d.   -- to go in that direction.
take(Object).            -- to pick up an object.
drop(Object).            -- to put down an object.
kill.                    -- to attack an enemy.
look.                    -- to look around you again.
instructions.            -- to see this message again.
halt.                    -- to end the game and quit.

You are in a meadow.  To the north is the dark mouth
of a cave; to the south is a small building.  Your
assignment, should you decide to accept it, is to
recover the famed Bar-Abzad ruby and return it to
this meadow.


start

?- n.
Go into that dark cave without a light?  Are you crazy?
You cannot go that way.n

?-
[download]

Shell commands in the aiprolog shell start with a percent sign '%' (which isn't too surprising as this is how you begin comments in Prolog.) The first command, % no more, tells the shell to not issue the More? (y/N) command after you issue queries. Usually you would want those, but when you're playing the game, it's quite annoying.

The second command, start., is a Prolog predicate defined in the program spider.pro. The commands that you issue to play the game are actually simple Prolog statements. You're learning logic programming and playing a game at the same time! Playing around with the shell, reading the docs and working through an easy guide to Prolog should be enough to get you started learning Prolog, though you really don't have to know it to play the game.

Just to give you an idea of how easy this is, here's the code to pick up (take) an object:

take(Object) :-
  i_am_at(Place),
  at(Object, Place),
  retract(at(Object, Place)),
  assert(at(Object, in_hand)),
  print('OK.'),
  nl.
[download]

The only thing that might be mysterious about that is "nl" and that's just a command to print a newline.

If you want to write your own games (or other sample programs), feel free to send them to me and they might make it into the next distribution. Also, patches, suggestions and requests welcome! I expect to do a lot more with AI::Prolog in the future and the more involvement, the merrier.

Note that the latest information about AI::Prolog is usually posted to my use.perl journal.