Solve 'Delta Bits' kata

Author: borisskert

src/DeltaBits.hs

@@ -0,0 +1,8 @@
+module DeltaBits (convertBits) where
+
+-- https://www.codewars.com/kata/538948d4daea7dc4d200023f/train/haskell
+
+import Data.Bits (Bits (popCount, xor))
+
+convertBits :: Int -> Int -> Int
+convertBits = (popCount .) . xor

src/SaveChristmas.hs

@@ -2,13 +2,13 @@ module SaveChristmas (determineTime) where
 
 -- https://www.codewars.com/kata/5857e8bb9948644aa1000246/train/haskell
 
-import Data.Maybe (fromJust, mapMaybe)
+import Data.Maybe (fromJust)
 import Data.Time (DiffTime, defaultTimeLocale, diffTimeToPicoseconds, parseTimeM)
 
 determineTime :: [String] -> Bool
 determineTime arr = needed <= oneDay
   where
-    needed = sum . map diffTimeToPicoseconds . mapMaybe readDiffTime $ arr :: Integer
+    needed = sum . map readPicoseconds $ arr :: Integer
     oneDay = readPicoseconds "24:00:00"
 
 readPicoseconds :: String -> Integer

test/DeltaBitsSpec.hs

@@ -0,0 +1,17 @@
+module DeltaBitsSpec (spec) where
+
+import DeltaBits (convertBits)
+import Test.HUnit (assertEqual)
+import Test.Hspec
+
+spec :: Spec
+spec = do
+  it "description example test" $ do
+    assertEqual "convertBits 31 14" 2 $ convertBits 31 14
+  it "more example tests" $ do
+    assertEqual "convertBits 7 17" 3 $ convertBits 7 17
+    assertEqual "convertBits 31 0" 5 $ convertBits 31 0
+    assertEqual "convertBits 0 0" 0 $ convertBits 0 0
+    assertEqual "convertBits 127681 127681" 0 $ convertBits 127681 127681
+    assertEqual "convertBits 312312312 5645657" 13 $ convertBits 312312312 5645657
+    assertEqual "convertBits 43 2009989843" 17 $ convertBits 43 2009989843