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| -rw-r--r-- | problem-9.scm | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/problem-9.scm b/problem-9.scm new file mode 100644 index 0000000..cc0b862 --- /dev/null +++ b/problem-9.scm @@ -0,0 +1,25 @@ +(use-modules (srfi srfi-1) + (srfi srfi-42)) + +(define (square x) + (* x x)) + +;; Euclid's formula. +(define (generate-triple n m) + (list (- (square n) (square m)) + (* 2 n m) + (+ (square n) (square m)))) + +(define (generate-triples max-n max-m) + (concatenate + (list-ec (:range n 2 max-n) + (list-ec (:range m 1 (1- n)) + (generate-triple n m))))) + +(define (find-triple-sum goal) + (find (lambda (triple) + (= (apply + triple) goal)) + ;; Assumed that this range would be enough. :) + (generate-triples 100 99))) + +(apply * (find-triple-sum 1000)) |