Use mrb_true_or_false_value() / in mrb_obj_not_equal_m().

src/kernel.c

@@ -108,14 +108,12 @@ static mrb_value
 mrb_obj_not_equal_m(mrb_state *mrb, mrb_value self)
 {
   mrb_value arg;
+  mrb_bool eql_p;
 
   mrb_get_args(mrb, "o", &arg);
-  if (mrb_equal(mrb, self, arg)) {
-    return mrb_false_value();
-  }
-  else {
-    return mrb_true_value();
-  }
+  eql_p = mrb_obj_equal(mrb, self, arg);
+
+  return mrb_true_or_false_value(!eql_p);
 }
 
 /* 15.3.1.3.2  */