Data commit

Task/Tau-number/Haskell/tau-number-1.hs

@@ -0,0 +1,15 @@
+tau :: Integral a => a -> a
+tau n | n <= 0 = error "Not a positive integer"
+tau n = go 0 (1, 1)
+    where
+    yo i = (i, i * i)
+    go r (i, ii)
+        | n < ii = r
+        | n == ii = r + 1
+        | 0 == mod n i = go (r + 2) (yo $ i + 1)
+        | otherwise = go r (yo $ i + 1)
+
+isTau :: Integral a => a -> Bool
+isTau n = 0 == mod n (tau n)
+
+main = print . take 100 . filter isTau $ [1..]

Task/Tau-number/Haskell/tau-number-2.hs

@@ -0,0 +1,33 @@
+import Data.List (group, scanl)
+import Data.List.Split (chunksOf)
+import Data.Numbers.Primes (primeFactors)
+
+----------------------- TAU NUMBERS ----------------------
+
+tauNumbers :: [Int]
+tauNumbers =
+  filter
+    ((0 ==) . (rem <*> (length . divisors)))
+    [1 ..]
+
+--------------------------- TEST -------------------------
+main :: IO ()
+main =
+  let xs = take 100 $ fmap show tauNumbers
+      w = length $ last xs
+   in (putStrLn . unlines) $
+        unwords . fmap (justifyRight w ' ')
+          <$> chunksOf 10 xs
+
+------------------------- GENERIC ------------------------
+
+divisors :: Int -> [Int]
+divisors =
+  foldr
+    (flip ((<*>) . fmap (*)) . scanl (*) 1)
+    [1]
+    . group
+    . primeFactors
+
+justifyRight :: Int -> Char -> String -> String
+justifyRight n c = (drop . length) <*> (replicate n c <>)