Euler-problem-8.scm

 (define 1000-digit 7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450)
 
(define 1000-ls (split-digit 1000-digit))
 
(define (split-digit n)
  (split-digit-iter n ()))
 
(define (split-digit-iter n a)
  (cond
   ((zero? n) a)
   (else
    (split-digit-iter (quotient n 10) (cons (modulo n 10) a)))))
 
(define (list-ref-ex ls n m)
  (cond
   ((zero? m) ())
   ((>= n (list-size ls)) ())
   (else
    (cons (list-ref ls n) (list-ref-ex ls (+ n 1) (- m 1))))))

(define (list-size ls)
  (cond
   ((null? ls) 0)
   (else
    (+ 1 (list-size (cdr ls))))))

(define (list-product ls)
  (cond
   ((null? ls) 1)
   (else
    (* (car ls) (list-product (cdr ls))))))

(define (greatest-iter max-value ls)
  (cond
   ((null? ls) max-value)
   ((> (list-product (list-ref-ex ls 0 5)) max-value)
    (greatest-iter (list-product (list-ref-ex ls 0 5)) (cdr ls)))
   (else
    (greatest-iter max-value (cdr ls)))))
    
(define (greatest-product ls)
  (greatest-iter 0 ls))

(greatest-product 1000-ls)