Lucas-Lehmer test: Difference between revisions

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 {{works with|GHC|6.8.2}}
- module Main
+<lang haskell>module Main
-   where
+  where
- main = printMersennes $ take 45 $ filter lucasLehmer $ sieve [2..]
+main = printMersennes $ take 45 $ filter lucasLehmer $ sieve [2..]
- s mp 1 = 4 `mod` mp
+s mp 1 = 4 `mod` mp
- s mp n = ((s mp $ n-1)^2-2) `mod` mp
+s mp n = ((s mp $ n-1)^2-2) `mod` mp
- lucasLehmer 2 = True
+lucasLehmer 2 = True
- lucasLehmer p = s (2^p-1) (p-1) == 0
+lucasLehmer p = s (2^p-1) (p-1) == 0
- printMersennes [] = return ()
+printMersennes = mapM_ (\x -> putStrLn $ "M" ++ show x)</lang>
- printMersennes (x:xs) = do putStrLn $ "M"++(show x)
-                            printMersennes xs
 It is pointed out on the [[Sieve of Eratosthenes]] page that the following "sieve" is inefficient. Nonetheless it takes very little time compared to the Lucas-Lehmer test itself.
- sieve (p:xs) = p : sieve [x | x <- xs, x `mod` p > 0]
+<lang haskell>sieve (p:xs) = p : sieve [x | x <- xs, x `mod` p > 0]</lang>
 It takes about 30 minutes to get up to:
+<pre>
- M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213
+M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213
+</pre>
 =={{header|J}}==