Text of the problem: 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.
My solution:
: million ( n -- n' ) 1000000 * ;
: fibonacci ( n -- seq ) 0 1 rot '[ dup _ < ] [ swap over + dup ] produce
2nip ; ! Where has "tuck" gone?!
4 million fibonacci [ even? ] filter sum
Any comments on how it can be simplified or made more idiomatic?
--
Cheers,
missingfaktor <http://twitter.com/#!/missingfaktor>.
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