?- solve(numbers(4,5,6,4,9),goal(0)).
NUMBERS = {4 5 6 4 9} GOAL = 0
considering rule 1 ...
considering rule 2 ...
considering rule 3 ...
application of rule 3 produces (  ( 4 - 4 ) * ( 5 *  ( 6 * 9 ) ) )
true .

?- solve(numbers(5,0,6,0,7),goal(0)).
NUMBERS = {5 0 6 0 7} GOAL = 0
considering rule 1 ...
application of rule 1 produces ( 5 * ( 0 * ( 6 *  ( 0 * 7 ) ) ) )
true ;
application of rule 1 produces ( 5 * ( 0 * ( 6 *  ( 0 * 7 ) ) ) )
true ;
considering rule 2 ...
considering rule 3 ...
application of rule 3 produces (  ( 0 - 0 ) * ( 5 *  ( 6 * 7 ) ) )
true.

?- solve(numbers(1,0,1,2,3),goal(0)).
NUMBERS = {1 0 1 2 3} GOAL = 0
considering rule 1 ...
application of rule 1 produces ( 1 * ( 0 * ( 1 *  ( 2 * 3 ) ) ) )
true ;
considering rule 2 ...
considering rule 3 ...
application of rule 3 produces (  ( 1 - 1 ) * ( 0 *  ( 2 * 3 ) ) )
true.