Warning: No rules/facts defined for relation B in file rule_arity.dl at line 4
.decl B (x:N)
------^-------
Warning: No rules/facts defined for relation C in file rule_arity.dl at line 5
.decl C (x:N)
------^-------
Warning: No rules/facts defined for relation D in file rule_arity.dl at line 6
.decl D (x:N)
------^-------
Error: Mismatching arity of relation B (expected 1, got 2) in file rule_arity.dl at line 8
A (x, y, z) :- B(x), C(y), D(z), B(x,y).
---------------------------------^-------
1 errors generated, evaluation aborted
