/* pete1.pl
 *
 * CS 313
 *
 * easy version of pete's puzzle solver
 */

solve(A, B, C, D) :-
	exp2(A, B, E1),
	exp2(C, D, E2),
	checkeq(E1, E2).

exp2(A, B, A+B).
exp2(A, B, A-B).
exp2(A, B, A*B).
exp2(A, B, A/B) :-
	B \= 0.

checkeq(E1, E2) :-
	R1 is E1,
	R2 is E2,
	R1 = R2,
	write_ln(E1 = E2).

/*      fail.   */

/* add 'fail' as last subgoal to print all solutions */