(Nils' Scheme Snippets)

Test whether a given property exists in a sequence of lists. The property is expressed using the n-ary predicate p. P is first applied to a list consisting of the first member of each given list. If p returns truth, exists returns #t immediately. Otherwise it is applied to a list consisting of the second member of each given list, etc. If p returns falsity for all sets of members, exists returns #f.

proc	predicate
a*	lists

(exists < '(9 1) '(8 2) '(7 3)) => #t
; because (< 1 2 3)

(define (exists p . a*)
  (letrec
    ((carof
       (lambda (a)
         (map car a)))
     (cdrof
       (lambda (a)
         (map cdr a)))
     (exists*
       (lambda (a*)
         (cond ((null? (car a*)) #f)
           (else (or (apply p (carof a*))
                     (exists* (cdrof a*))))))))
    (exists* a*)))