Initial data commit

Task/Almost-prime/Haskell/almost-prime-1.hs

@@ -0,0 +1,18 @@
+isPrime :: Integral a => a -> Bool
+isPrime n = not $ any ((0 ==) . (mod n)) [2..(truncate $ sqrt $ fromIntegral n)]
+
+primes :: [Integer]
+primes = filter isPrime [2..]
+
+isKPrime :: (Num a, Eq a) => a -> Integer -> Bool
+isKPrime 1 n = isPrime n
+isKPrime k n = any (isKPrime (k - 1)) sprimes
+  where
+    sprimes = map fst $ filter ((0 ==) . snd) $ map (divMod n) $ takeWhile (< n) primes
+
+kPrimes :: (Num a, Eq a) => a -> [Integer]
+kPrimes k = filter (isKPrime k) [2..]
+
+main :: IO ()
+main = flip mapM_ [1..5] $ \k ->
+  putStrLn $ "k = " ++ show k ++ ": " ++ (unwords $ map show (take 10 $ kPrimes k))

Task/Almost-prime/Haskell/almost-prime-2.hs

@@ -0,0 +1,27 @@
+primes = 2:3:[n | n <- [5,7..], foldr (\p r-> p*p > n || rem n p > 0 && r)
+	True (drop 1 primes)]
+
+merge aa@(a:as) bb@(b:bs)
+	| a < b = a:merge as bb
+	| otherwise = b:merge aa bs
+
+-- n-th item is all k-primes not divisible by any of the first n primes
+notdivs k = f primes $ kprimes (k-1) where
+	f (p:ps) s = map (p*) s : f ps (filter ((/=0).(`mod`p)) s)
+
+kprimes k
+	| k == 1 = primes
+	| otherwise = f (head ndk) (tail ndk) (tail $ map (^k) primes) where
+		ndk = notdivs k
+		-- tt is the thresholds for merging in next sequence
+		-- it is equal to "map head seqs", but don't do that
+		f aa@(a:as) seqs tt@(t:ts)
+			| a < t = a : f as seqs tt
+			| otherwise = f (merge aa $ head seqs) (tail seqs) ts
+
+main = do
+	-- next line is for task requirement:
+	mapM_ (\x->print (x, take 10 $ kprimes x)) [1 .. 5]
+
+	putStrLn "\n10000th to 10100th 500-amost primes:"
+	mapM_ print $ take 100 $ drop 10000 $ kprimes 500