gistfile1.scm

(load "mkprelude.scm")

(define peanoo
  (lambda (n out)
    (conde
      [(== n (build-num 0)) (== '(O) out)]
      [(fresh (n1 res)
         (-o n (build-num 1) n1)
         (conso 'S res out)
         (peanoo n1 res))])))

(test "peanoo-1"
  (run 1 (q) (peanoo (build-num 0) q))
  '((O)))

(test "peanoo-2"
  (run 1 (q) (peanoo (build-num 3) q))
  '((S S S O)))

(test "peanoo-3"
  (run 1 (q) (peanoo q '(O)))
  '(()))

(test "peanoo-4"
  (run 1 (q) (peanoo q '(S S S O)))
  '((1 1)))

(define-syntax test
  (syntax-rules ()
    ((_ title tested-expression expected-result)
     (let* ((expected expected-result)
            (produced tested-expression))
       (if (equal? expected produced)
           (printf "~s works!\n" title)
           (error
            'test
            "Failed ~s: ~a\nExpected: ~a\nComputed: ~a"
            title 'tested-expression expected produced))))))