Clean up build warnings

Issue 170, implement PR comments and clean up build warnings

Author: kayvank

dataframe.cabal

@@ -106,7 +106,6 @@ library
                       process ^>= 1.6,
                       snappy-hs ^>= 0.1,
                       random >= 1.2 && < 1.3,
-                      random-shuffle >= 0.0.4 && < 1,
                       regex-tdfa >= 1.3.0 && < 2,
                       scientific >=0.3.1 && <0.4,
                       template-haskell >= 2.0 && < 3,

src/DataFrame/Operations/Permutation.hs

@@ -77,17 +77,19 @@ shuffle pureGen df =
         df{columns = V.map (atIndicesStable indexes) (columns df)}
 
 shuffledIndices :: (RandomGen g) => g -> Int -> VU.Vector Int
-shuffledIndices pureGen k = shuffleVec pureGen (VU.fromList [0 .. (k - 1)])
+shuffledIndices pureGen k
+    | k <= 0 = VU.empty
+    | otherwise = shuffleVec pureGen
   where
-    shuffleVec :: (RandomGen g) => g -> VU.Vector Int -> VU.Vector Int
-    shuffleVec g v = runST $ do
-        vm <- VU.thaw v
-        let (n, nGen) = randomR (0, (k - 1)) g
+    shuffleVec :: (RandomGen g) => g -> VU.Vector Int
+    shuffleVec g = runST $ do
+        vm <- VUM.generate k id
+        let (n, nGen) = randomR (1, (k - 1)) g
         go vm n nGen
         VU.unsafeFreeze vm
 
     go v (-1) _ = pure ()
     go v 0 _ = pure ()
     go v maxInd gen =
-        let (n, nextGen) = randomR (0, maxInd) gen
+        let (n, nextGen) = randomR (1, maxInd) gen
          in VUM.swap v 0 n *> go (VUM.tail v) (maxInd - 1) nextGen