repeat
Nondetermenistic loop.
Remark
The predicate repeat will always succeed, but because of its nondeterminism it will raise the new subgoal at the each loop. repeat is defined as:
repeat. repeat :- repeat.
Usualy the repeat is used for the fail-controlled loops.
Example
loop :- repeat, write ("Yet more loop ?"), read (YN), (YN = "N";YN="n").