[vox-tech] entering a prolog program?

[Brian Lavender]

Can you type in axioms into prolog from the command line? All I seem to
be able to do is load a program and query it. 

Can I just enter the following program at the prolog prompt?

factorial(0,1).
  
factorial(A,B) :-  
           A > 0, 
           C is A-1,
           factorial(C,D),
           B is A*D. 


All I seem to be able to do is load it. I am using SWI prolog.

$ swipl
?- ['factorial.pl'].
true.

If I try the following, I get an error. 

?- factorial(0, 1).
ERROR: toplevel: Undefined procedure: factorial/2 (DWIM could not correct goal)

brian
-- 
Brian Lavender
http://www.brie.com/brian/

"Program testing can be used to show the presence of bugs, but never to
show their absence!"

Professor Edsger Dijkstra
1972 Turing award recipient