Solve problem 8.

1 files changed, 21 insertions, 0 deletions

diff --git a/problem-8.scm b/problem-8.scm
new file mode 100644
index 0000000..a9b94d5
--- /dev/null
+++ b/problem-8.scm
@@ -0,0 +1,21 @@
+(use-modules (srfi srfi-1)
+             (srfi srfi-42))
+
+(define big-ass-number
+  "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450")
+
+(define (digit str i)
+  (string->number (substring str i (1+ i))))
+
+(define (five-digits numstring start)
+  (list (digit numstring start)
+        (digit numstring (+ start 1))
+        (digit numstring (+ start 2))
+        (digit numstring (+ start 3))
+        (digit numstring (+ start 4))))
+
+(define (five-digit-products numstring)
+  (list-ec (: i (- (string-length numstring) 6))
+           (apply * (five-digits numstring i))))
+
+(reduce max 0 (five-digit-products big-ass-number))