test/99.lisp @ 3325913a9b16

(in-package #:bones-test.99)

;;;; 99 Prolog Problems
;;; http://www.ic.unicamp.br/~meidanis/courses/mc336/2009s2/prolog/problemas/
;;;
;;; Solutions to at least a few of these, for testing purposes.


(defun %= ()
  (push-logic-frame-with
    (fact (= ?x ?x))))

(defun %not ()
  (push-logic-frame-with
    (rule (not ?x) (call ?x) ! fail)
    (fact (not ?x))))

(defun %append ()
  (push-logic-frame-with
    (fact (append nil ?l ?l))
    (rule (append (list* ?x ?rest) ?l (list* ?x ?result))
      (append ?rest ?l ?result))))


(test p1
  ;; Find the last element of a list.
  (with-fresh-database
    (push-logic-frame-with
      (fact (last ?x (list ?x)))
      (rule (last ?x (list* ? ?tail))
        (last ?x ?tail)))

    (should-return
      ((last a (list a b c)) fail)
      ((last b (list a b c)) fail)
      ((last c (list a b c)) empty)

      ((last ?what nil) fail)
      ((last ?what (list a))
       (?what a))

      ((last ?what (list (h x) (f (g x))))
       (?what (f (g x))))

      ((last ?what (list (list foo)))
       (?what (foo))))))


(test p2
  ;; Find the last but one element of a list.
  (with-fresh-database
    (push-logic-frame-with
      (fact (last-but-one ?x (list ?x ?)))
      (rule (last-but-one ?x (list* ? ?tail))
        (last-but-one ?x ?tail)))

    (should-return
      ((last-but-one a (list a b c)) fail)
      ((last-but-one b (list a b c)) empty)
      ((last-but-one c (list a b c)) fail)

      ((last-but-one ?what nil) fail)
      ((last-but-one c (list a b c d)) empty)

      ((last-but-one ?what (list (h x) (f (g x))))
       (?what (h x)))

      ((last-but-one ?what (list (list foo) (list bar)))
       (?what (foo))))))


;;; TODO: p3/p4 when we have maths


(defun %reverse ()
  (push-logic-frame-with
    (fact (reverse-acc nil ?acc ?acc))
    (rule (reverse-acc (list* ?x ?tail) ?acc ?reversed)
      (reverse-acc ?tail (list* ?x ?acc) ?reversed))

    (rule (reverse ?l ?r)
      (reverse-acc ?l nil ?r))))

(test p5
  ;; Reverse a list.
  (with-fresh-database
    (%reverse)

    (should-return
      ((reverse nil nil) empty)
      ((reverse (list 1) nil) fail)
      ((reverse (list 1) (list 1)) empty)
      ((reverse (list 1 2) (list 2 1)) empty)
      ((reverse (list (f foo) (f bar))
                (list (f bar) (f foo)))
       empty)
      ((reverse (list ?x 2 3 4)
                (list ?y 3 2 1))
       (?x 1 ?y 4)))))


(test p6
  ;; Find out whether a list is a palindrome.
  (with-fresh-database
    (%reverse)
    (push-logic-frame-with
      (rule (palindrome ?l)
        (reverse ?l ?l)))

    (should-return
      ((palindrome nil) empty)
      ((palindrome (list 1)) empty)
      ((palindrome (list 1 1)) empty)
      ((palindrome (list 1 2)) fail)
      ((palindrome (list 1 2 1)) empty)
      ((palindrome (list (f foo) ?what))
       (?what (f foo))))))


(test p7
  ;; Flatten a nested list structure.
  (with-fresh-database
    (%not)
    (%append)

    (push-logic-frame-with
      (fact (is-list nil))
      (fact (is-list (list* ? ?)))

      (fact (flatten nil nil))

      (rule (flatten (list* ?atom ?tail)
                     (list* ?atom ?flat-tail))
        (not (is-list ?atom))
        (flatten ?tail ?flat-tail))

      (rule (flatten (list* ?head ?tail) ?flattened)
        (is-list ?head)
        (flatten ?head ?flat-head)
        (flatten ?tail ?flat-tail)
        (append ?flat-head ?flat-tail ?flattened)))

    (should-return
      ((is-list nil) empty)
      ((is-list (list a)) empty)
      ((is-list (list a b)) empty)
      ((is-list (f x)) fail)
      ((is-list a) fail)

      ((flatten nil ?what)
       (?what nil))

      ((flatten (list a) ?what)
       (?what (a)))

      ((flatten (list (list a)) ?what)
       (?what (a)))

      ((flatten (list (list a b) (list (list c))) ?what)
       (?what (a b c))))))


(test p8
  ;; Eliminate consecutive duplicates of list elements.
  (with-fresh-database
    (%=)
    (%not)

    (push-logic-frame-with
      (fact (compress nil nil))
      (fact (compress (list ?x) (list ?x)))

      (rule (compress (list* ?x ?x ?rest) ?result)
        (compress (list* ?x ?rest) ?result))

      (rule (compress (list* ?x ?y ?rest) (list* ?x ?result))
        (not (= ?x ?y))
        (compress (list* ?y ?rest) ?result)))

    (should-return
      ((compress nil ?what)
       (?what nil))

      ((compress (list a) ?what)
       (?what (a)))

      ((compress (list a b c) ?what)
       (?what (a b c)))

      ((compress (list a b b a) ?what)
       (?what (a b a)))

      ((compress (list (f cats ?) ?what (f ? dogs))
                 (list ?))
       (?what (f cats dogs))))))