21 lines
615 B
Haskell
21 lines
615 B
Haskell
-- 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:
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--
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-- 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
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--
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-- By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
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fib :: Int -> Int
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fib 0 = 0
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fib 1 = 1
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fib n = fib (n - 1) + fib (n - 2)
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sumEvenFib :: Int
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sumEvenFib = sum $ filter even $ takeWhile (<= 4000000) (map fib [0 ..])
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main = do
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let result = sumEvenFib
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putStrLn $
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"Project Euler, Problem 2\n"
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++ "Answer: "
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++ show result
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