Data commit

Task/N-smooth-numbers/Haskell/n-smooth-numbers.hs

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+import Data.Numbers.Primes (primes)
+import Text.Printf (printf)
+
+
+merge :: Ord a => [a] -> [a] -> [a]
+merge [] b = b
+merge a@(x:xs) b@(y:ys) | x < y     = x : merge xs b
+                        | otherwise = y : merge a ys
+
+nSmooth :: Integer -> [Integer]
+nSmooth p = 1 : foldr u [] factors
+ where
+   factors = takeWhile (<=p) primes
+   u n s = r
+    where r = merge s (map (n*) (1:r))
+
+main :: IO ()
+main = do
+  mapM_ (printf "First 25 %d-smooth:\n%s\n\n" <*> showTwentyFive) firstTenPrimes
+  mapM_
+    (printf "The 3,000 to 3,202 %d-smooth numbers are:\n%s\n\n" <*> showRange1)
+    firstTenPrimes
+  mapM_
+    (printf "The 30,000 to 30,019 %d-smooth numbers are:\n%s\n\n" <*> showRange2)
+    [503, 509, 521]
+  where
+    firstTenPrimes = take 10 primes
+    showTwentyFive = show . take 25 . nSmooth
+    showRange1 = show . ((<$> [2999 .. 3001]) . (!!) . nSmooth)
+    showRange2 = show . ((<$> [29999 .. 30018]) . (!!) . nSmooth)