




The Common Prolog system comes with a built-in 
read-query-print
 loop similar to a Prolog interpreter loop. To run it, make sure the common-prolog package is accessible and type: 
(rqp)
. You will be presented with the prompt: 
==>
. At this point you may type in goal expressions, for example: 
|==> (append ?x ?y (1 2))
|
|?X = NIL
|?Y = (1 2)
Now Common Prolog is waiting for you to indicate whether or not you wish more solutions. If you press 
Return
, you will get the message 
OK
 and return to the top level:
|?X = NIL
|?Y = (1 2)<RETURN>
|
|OK.
|
|==>