Created
April 23, 2015 17:51
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-- 本に載っていたコードは大体Qiitaに書いてしまったので、趣味で書いてみた円周率の計算コードを幾つか | |
-- 効率とかは気にしていないので収束はかなり遅い | |
-- ライプニッツの公式 | |
4 * (sum (take 2000 (zipWith (/) (iterate negate 1) [1,3..]))) | |
-- ウォリス積 | |
2 * (product $ take 2000 $ zipWith (/) (concat $ map (replicate 2) [2, 4..]) (tail.concat $ map (replicate 2) [1, 3..])) | |
-- バーゼル問題(zeta(2) = π^2 / 6) オイラーさんマジ天才 | |
sqrt $ 6 * (sum $ take 2000 $ map (1/) $ map (^2) [1..]) | |
-- バーゼル問題(zeta(4) = π^4 / 90) | |
sqrt.sqrt $ 90 * (sum $ take 2000 $ map (1/) $ map (^4) [1..]) | |
-- 調子に乗ってネイピア数も計算してみた | |
let factorial n = if n == 0 then 1 else n * factorial (n - 1) | |
-- exp(x)のテイラー展開 | |
sum $ take 2000 $ map (1/) $ map factorial [1..] |
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