I am trying to run a simple gprologlauncher on my Linux machine, GNU Prolog was installed from the Ubuntu Software Center.
From GNU Prolog Intro I got the following example saved in HelloWorld.pl.
parent(hank,ben).
parent(hank,denise).
parent(irene,ben).
parent(irene,denise).
parent(alice,carl).
parent(ben,carl).
parent(denise,frank).
parent(denise,gary).
parent(earl,frank).
parent(earl,gary).
grandparent(X,Z):-parent(X,Y),parent(Y,Z).
ancestor(X,Y):-parent(X,Y).
ancestor(X,Y):-parent(Z,Y),ancestor(X,Z).
Run gprolog, enter [HelloProlog].and get the following error:
| ?- [HelloProlog].
uncaught exception: error(instantiation_error,consult/1)
Even if I don’t download the code from the file, but run it interactively, I get an error message:
uwe@z11:~/desktop$ gprolog
GNU Prolog 1.3.0
By Daniel Diaz
Copyright (C) 1999-2007 Daniel Diaz
| ?- parent(Luke,Anakin).
uncaught exception: error(existence_error(procedure,parent/2),top_level/0)
| ?-
Is my installation working or what am I doing wrong?