The negation as failure constraint {{nafc}} is supposed to succeed if and only if the goal provided by a relation and its args fails. The test cases just cover very simple cases like {{(nafc == q 'b)}} which is essentially equivalent to `(!= q 'b)`

(at least to my understanding). But with a slightly more complex case, it doesn't seem to work anymore.

Example:

```

(run* [q]

(fresh [a b]

```
(== q (list a b))
(fd/in a b (fd/interval 1 3)) ;; fd is an alias for clojure.core.logic.fd
(fd/< a b)
(nafc membero 2 q)))
```

;=> ((1 2) (2 3) (1 3))

```

The constraint specifies that the number 2 must NOT be contained in the list {{q}} but still it is. I expected to get the single answer {{(1 3)}} here.