mk-notes.scm

(define menu
  (lambda (x y)
    (conde
     [(== x 'tea) (== y 'biscuit)]
     [(== x 'coffee) (== y 'cookie)])))

(define conso
  (lambda (x y o)
    (== `(,x . ,y) o)))

(define child
  (lambda (x y)
    (conde
     [(== 'Mary x) (== 'Richard y)]
     [(== 'Richard x) (== 'Leslie y)]
     [(== 'Emma x) (== 'Helen y)]
     [(== 'Sophie x) (== 'Helen y)])))

(define male
  (lambda (x)
    (conde
     [(== 'Leslie x)]
     [(== 'Richard x)])))

(define female
  (lambda (x)
    (conde
     [(== 'Emma x)]
     [(== 'Sophie x)]
     [(== 'Helen x)]
     [(== 'Mary x)])))

(define son
  (lambda (x y)
    (fresh ()
      (male x)
      (child x y))))

(define daughter
  (lambda (x y)
    (fresh ()
      (female x)
      (child x y))))

(define grandchild
  (lambda (x y)
    (fresh (z)
      (child x z)
      (child z y))))

(define right
  (lambda (x y l)
    (conde
     [(fresh (z)
        (== `(,x ,y . ,z) l))]
     [(fresh (a z)
        (== `(,a . ,z) l)
        (right x y z))])))

(define next
  (lambda (x y l)
    (conde
     [(right x y l)]
     [(right y x l)])))

(define nevero
  (lambda ()
    (fresh ()
      (nevero))))