Data commit

Task/Population-count/Haskell/population-count-1.hs

@@ -0,0 +1,10 @@
+import Data.Bits (popCount)
+
+printPops :: (Show a, Integral a) => String -> [a] -> IO ()
+printPops title counts = putStrLn $ title ++ show (take 30 counts)
+
+main :: IO ()
+main = do
+  printPops "popcount " $ map popCount $ iterate (*3) (1 :: Integer)
+  printPops "evil     " $ filter (even . popCount) ([0..] :: [Integer])
+  printPops "odious   " $ filter ( odd . popCount) ([0..] :: [Integer])

Task/Population-count/Haskell/population-count-2.hs

@@ -0,0 +1,22 @@
+import Data.Bifoldable (biList)
+import Data.List (partition, unfoldr)
+import Data.Tuple (swap)
+
+--------------------- POPULATION COUNT -------------------
+popCount :: Int -> Int
+popCount = sum . unfoldr go
+  where
+    go x
+      | 0 < x = (Just . swap) (quotRem x 2)
+      | otherwise = Nothing
+
+--------------------------- TEST -------------------------
+main :: IO ()
+main =
+  mapM_ putStrLn $
+    zipWith
+      (\k xs -> concat [k, ":\n", show xs, "\n"])
+      ["Population count of powers of 3", "evil", "odious"]
+      ( (popCount . (3 ^) <$> [0 .. 29]) :
+        biList (partition (even . popCount) [0 .. 59])
+      )