The Great Packaging

author |
Steve Losh <steve@stevelosh.com> |

date |
Sat, 15 Dec 2018 17:25:12 -0500 |

parents |
(none) |

children |
(none) |

(defpackage :euler/002 #.euler:*use*)
(in-package :euler/002)
;; Each new term in the Fibonacci sequence is generated by adding the previous
;; two terms. By starting with 1 and 2, the first 10 terms will be:
;;
;; 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
;;
;; By considering the terms in the Fibonacci sequence whose values do not exceed
;; four million, find the sum of the even-valued terms.
(define-problem (2 4613732)
(iterate (for n :in-fibonacci t)
(while (<= n 4000000))
(when (evenp n)
(summing n))))