diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6d910ee
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,25 @@
+# Created by https://www.gitignore.io/api/haskell
+
+### Haskell ###
+dist
+dist-*
+cabal-dev
+*.o
+*.hi
+*.chi
+*.chs.h
+*.dyn_o
+*.dyn_hi
+.hpc
+.hsenv
+.cabal-sandbox/
+cabal.sandbox.config
+*.prof
+*.aux
+*.hp
+*.eventlog
+.stack-work/
+cabal.project.local
+.HTF/
+
+# End of https://www.gitignore.io/api/haskell
diff --git a/ChangeLog.md b/ChangeLog.md
new file mode 100644
index 0000000..3a52c4a
--- /dev/null
+++ b/ChangeLog.md
@@ -0,0 +1,5 @@
+# Revision history for CtCI-6th-Edition-Haskell
+
+## 0.1.0.0  -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.
diff --git a/CtCI-6th-Edition-Haskell.cabal b/CtCI-6th-Edition-Haskell.cabal
new file mode 100644
index 0000000..c8d2297
--- /dev/null
+++ b/CtCI-6th-Edition-Haskell.cabal
@@ -0,0 +1,121 @@
+name:                CtCI-6th-Edition-Haskell
+version:             0.1.0.0
+synopsis:            Haskell Solutions for Cracking the Coding Interview 6th Edition
+
+-- description:         
+
+homepage:            https://github.com/careercup/CtCI-6th-Edition-Haskell
+bug-reports:         https://github.com/careercup/CtCI-6th-Edition-Haskell/issues
+-- license:             
+license-file:        LICENSE
+author:              Variuos Contributors
+maintainer:          NA
+-- copyright:           
+-- category:            
+build-type:          Simple
+cabal-version:       >= 1.10
+tested-with:         GHC == 8.0.*
+
+extra-source-files:
+    ChangeLog.md
+  , LICENSE
+  , README.md
+  , Setup.hs
+
+source-repository head
+  type:     git
+  location: https://github.com/careercup/CtCI-6th-Edition-Haskell
+
+library
+  default-language:    Haskell2010
+
+  ghc-options:         -Wall -fwarn-tabs -fwarn-monomorphism-restriction
+                       -fwarn-unused-do-bind
+
+  hs-source-dirs:
+      src
+
+  exposed-modules:
+      Introduction.VI.Example01
+
+  other-modules:       
+
+  build-depends:
+      base == 4.9.*
+
+  other-extensions:
+
+test-suite CtCI-6th-Edition-Haskell-Tests
+  default-language:    Haskell2010
+  type:                exitcode-stdio-1.0
+  main-is:             Spec.hs
+
+  ghc-options:         -Wall -fwarn-tabs -fwarn-monomorphism-restriction
+                       -fwarn-unused-do-bind
+
+  hs-source-dirs:
+      src
+    , test
+
+  other-modules:
+      Introduction.VI.Example01
+    , Introduction.VI.Example01Spec
+
+  build-tool-depends:
+      hspec-discover:hspec-discover == 2.4.*
+
+  build-depends:
+      base       == 4.9.*
+    , hspec      == 2.4.*
+    , QuickCheck == 2.9.*
+
+  other-extensions:
+
+test-suite tests
+  default-language:    Haskell2010
+  type:                exitcode-stdio-1.0
+  main-is:             Main.hs
+
+  ghc-options:         -Wall -fwarn-tabs -fwarn-monomorphism-restriction
+                       -fwarn-unused-do-bind
+
+  hs-source-dirs:
+      src
+    , src/chapter-1
+    , src/chapter-2
+    , src/chapter-3
+
+  other-modules:
+--      Ch1
+--    , Ch2
+--    , Ch3
+--    , Data.Queue
+--    , Data.Stack
+--    , find-cycle
+--    , intersection
+--    , is-palindrome
+--    , is-permutation
+--    , is-rotation
+--    , is-unique
+--    , kth-last
+--    , one-away
+--    , palindrome-permutation
+--    , partition
+--    , Questions.MinStack
+--    , remove-dups
+--    , remove-node
+--    , rotate-matrix
+--    , string-compression
+--    , sum-lists
+--    , Test.MinStack
+--    , Test.Queue
+--    , Test.Stack
+--    , url-encode
+--    , zero-matrix
+
+  build-depends:
+      base
+    , hspec
+    , QuickCheck
+
+  other-extensions:
diff --git a/haskell-solutions.cabal b/haskell-solutions.cabal
deleted file mode 100644
index 7f3daf9..0000000
--- a/haskell-solutions.cabal
+++ /dev/null
@@ -1,83 +0,0 @@
--- Initial haskell-solutions.cabal generated by cabal init.  For further 
--- documentation, see http://haskell.org/cabal/users-guide/
-
--- The name of the package.
-name:                haskell-solutions
-
--- The package version.  See the Haskell package versioning policy (PVP) 
--- for standards guiding when and how versions should be incremented.
--- http://www.haskell.org/haskellwiki/Package_versioning_policy
--- PVP summary:      +-+------- breaking API changes
---                   | | +----- non-breaking API additions
---                   | | | +--- code changes with no API change
-version:             0.1.0.0
-
--- A short (one-line) description of the package.
--- synopsis:            
-
--- A longer description of the package.
--- description:         
-
--- The license under which the package is released.
--- license:             
-
--- The file containing the license text.
-license-file:        LICENSE
-
--- The package author(s).
-author:              various contributors
-
--- An email address to which users can send suggestions, bug reports, and 
--- patches.
-maintainer:          none
-
--- A copyright notice.
--- copyright:           
-
--- category:            
-
-build-type:          Simple
-
--- Extra files to be distributed with the package, such as examples or a 
--- README.
--- extra-source-files:  
-
--- Constraint on the version of Cabal needed to build this package.
-cabal-version:       >=1.10
-
-
-library
-  -- Modules exported by the library.
-  exposed-modules:     Main
-  
-  -- Modules included in this library but not exported.
-  -- other-modules:       
-  
-  -- LANGUAGE extensions used by modules in this package.
-  -- other-extensions:    
-  
-  -- Other library packages from which modules are imported.
-  build-depends:       base >=4.8 && <4.9
-                     , hspec
-                     , QuickCheck
-
-  -- Directories containing source files.
-  hs-source-dirs:      src
-                     , src/chapter-1
-                     , src/chapter-2
-                     , src/chapter-3
---                     , src/chapter-4
-  
-  -- Base language which the package is written in.
-  default-language:    Haskell2010
-  
-test-suite tests
-  ghc-options:      -Wall -fno-warn-orphans
-  type:             exitcode-stdio-1.0
-  main-is:          Main.hs
-  hs-source-dirs:   .
-  build-depends:    base
-                  , hspec
-                  , QuickCheck
-
-  default-language: Haskell2010
\ No newline at end of file
diff --git a/src/Introduction/VI/Example01.hs b/src/Introduction/VI/Example01.hs
new file mode 100644
index 0000000..3f60363
--- /dev/null
+++ b/src/Introduction/VI/Example01.hs
@@ -0,0 +1,14 @@
+{-|
+Module      : Introduction.VI.Example01
+Description : Introduction VI (Big O) Example 1 on Page 40
+-}
+module Introduction.VI.Example01 where
+
+import Prelude hiding (sum)
+
+sum :: Int -> Int
+sum n | n <= 0    = 0
+      | otherwise = n + sum (n - 1)
+
+main :: IO ()
+main = print $ sum 4
diff --git a/src/Main.hs b/src/Main.hs
index aff7163..b0f11df 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -1,7 +1,5 @@
 module Main where
 
-import Test.Hspec
-import Test.QuickCheck
 import Ch1
 import Ch2
 import Ch3
diff --git a/src/chapter-1/Ch1.hs b/src/chapter-1/Ch1.hs
index 1e6845f..4629786 100644
--- a/src/chapter-1/Ch1.hs
+++ b/src/chapter-1/Ch1.hs
@@ -1,10 +1,8 @@
 module Ch1 where
 
-import Test.QuickCheck
 import Test.Hspec
 
 ch1 :: IO ()
-ch1 = hspec $ do
-  describe "_______________________Chapter 1 tests_______________________" $ do
-    it "should have tests" $ do
-      True
+ch1 = hspec $
+  describe "_______________________Chapter 1 tests_______________________" $
+    it "should have tests" True
diff --git a/src/chapter-1/one-away.hs b/src/chapter-1/one-away.hs
index ce36d70..3d35439 100644
--- a/src/chapter-1/one-away.hs
+++ b/src/chapter-1/one-away.hs
@@ -3,7 +3,7 @@ oneAway a b = a `elem` candidates
   where candidates = deletes ++ transposes ++ replaces ++ inserts
         strlen = 1 + length b
         splits = zipWith splitAt [0..strlen] (replicate strlen b)
-        deletes = [x ++ (tail y) | (x, y) <- splits, length y > 0]
+        deletes = [x ++ tail y | (x, y) <- splits, not (null y)]
         transposes = [x ++ head t : head y : tail t | (x, y) <- splits, length y > 1, let t = tail y]
-        replaces = [x ++ c : (tail y) | (x, y) <- splits, c <- ['a'..'z'], length y > 0]
+        replaces = [x ++ c : tail y | (x, y) <- splits, c <- ['a'..'z'], not (null y)]
         inserts = [x ++ c : y | (x, y) <- splits, c <- ['a'..'z']]
diff --git a/src/chapter-1/zero-matrix.hs b/src/chapter-1/zero-matrix.hs
index 84ee5c0..73a6711 100644
--- a/src/chapter-1/zero-matrix.hs
+++ b/src/chapter-1/zero-matrix.hs
@@ -4,7 +4,7 @@ zeroMatrix :: [[Integer]] -> [[Integer]]
 zeroMatrix x = [[zero i j v | (j, v) <- zip [0..] row] | (i, row) <- zip [0..] x]
   where zeroRows = zeroIndices x
         zeroCols = zeroIndices $ transpose x
-        zeroIndices y = map fst $ filter snd $ zip [0..] (map (any (== 0)) y)
+        zeroIndices y = map fst $ filter snd $ zip [0..] (map (elem 0) y)
         zero row col val | row `elem` zeroRows = 0
                          | col `elem` zeroCols = 0
                          | otherwise = val
diff --git a/src/chapter-2/Ch2.hs b/src/chapter-2/Ch2.hs
index 7b6eedc..4de5c8a 100644
--- a/src/chapter-2/Ch2.hs
+++ b/src/chapter-2/Ch2.hs
@@ -1,11 +1,9 @@
 module Ch2 where
 
-import Test.QuickCheck
 import Test.Hspec
 
 ch2 :: IO ()
-ch2 = hspec $ do
-  describe "_______________________Chapter 2 tests_______________________" $ do
-    it "should have tests" $ do
-      True
+ch2 = hspec $
+  describe "_______________________Chapter 2 tests_______________________" $
+    it "should have tests" True
 
diff --git a/src/chapter-3/Ch3.hs b/src/chapter-3/Ch3.hs
index c43951a..a45f9ec 100644
--- a/src/chapter-3/Ch3.hs
+++ b/src/chapter-3/Ch3.hs
@@ -1,13 +1,12 @@
 module Ch3 where
 
-import Test.QuickCheck
 import Test.Hspec
 import Test.Stack
 import Test.Queue
 import Test.MinStack
 
 ch3 :: IO ()
-ch3 = hspec $ do
+ch3 = hspec $
   describe "_______________________Chapter 3 tests_______________________" $ do
     testStack
     testQueue
diff --git a/src/chapter-3/Data/Queue.hs b/src/chapter-3/Data/Queue.hs
index a3a3edb..58e0dca 100644
--- a/src/chapter-3/Data/Queue.hs
+++ b/src/chapter-3/Data/Queue.hs
@@ -6,7 +6,7 @@ instance Eq a => Eq (Queue a) where
   (==) a b = let a' = reorder a
                  b' = reorder b
              in checkEq a' b'
-             where checkEq (Queue xs ys) (Queue xs' ys') = ys == ys'
+             where checkEq (Queue _ ys) (Queue _ ys') = ys == ys'
 
 mkQueue :: a -> Queue a
 mkQueue a = Queue [a] []
@@ -16,18 +16,18 @@ enqueue a (Queue xs ys) = Queue (a:xs) ys
 
 dequeue :: Queue a -> Queue a
 dequeue q = case reorder q of 
-  (Queue xs (y:ys)) -> Queue xs ys
-  otherwise -> reorder q
+  (Queue xs (_:ys)) -> Queue xs ys
+  _                 -> reorder q
 
 peek :: Queue a -> Maybe a
 peek a = case reorder a of
-  (Queue _ (y:ys)) -> Just y
-  otherwise        -> Nothing
+  (Queue _ (y:_)) -> Just y
+  _                -> Nothing
 
 isEmpty :: Queue a -> Bool
 isEmpty (Queue [] []) = True
 isEmpty (Queue _ _ )  = False
 
 reorder :: Queue a -> Queue a
-reorder q@(Queue xs (y:ys)) = q
 reorder (Queue xs []) = Queue [] (reverse xs)
+reorder q = q
diff --git a/src/chapter-3/Data/Stack.hs b/src/chapter-3/Data/Stack.hs
index b82a39a..ba88a4b 100644
--- a/src/chapter-3/Data/Stack.hs
+++ b/src/chapter-3/Data/Stack.hs
@@ -1,22 +1,22 @@
 module Data.Stack where
 
-data Stack a = Stack [a]
+newtype Stack a = Stack [a]
   deriving (Eq, Show)
 
 push :: a -> Stack a -> Stack a
 push a (Stack xs) = Stack (a:xs)
 
 pop :: Stack a -> Stack a
-pop (Stack (x:xs)) = Stack xs
+pop (Stack (_:xs)) = Stack xs
 pop (Stack []) = Stack []
 
 peek :: Stack a -> Maybe a
-peek (Stack (x:xs)) = Just x
+peek (Stack (x:_)) = Just x
 peek (Stack []) = Nothing
 
 isEmpty :: Stack a -> Bool
 isEmpty (Stack []) = True
-isEmpty (Stack xs) = False
+isEmpty (Stack _)  = False
 
 mkStack :: a -> Stack a
 mkStack a = Stack [a]
diff --git a/src/chapter-3/Questions/MinStack.hs b/src/chapter-3/Questions/MinStack.hs
index 31d4aa2..30a1f49 100644
--- a/src/chapter-3/Questions/MinStack.hs
+++ b/src/chapter-3/Questions/MinStack.hs
@@ -11,7 +11,7 @@ data MinStack a = MinStack (S.Stack a) (S.Stack a)
 
 push :: Ord a => a -> MinStack a -> MinStack a
 push a (MinStack s1 (S.Stack [])) = MinStack (S.push a s1) (S.mkStack a)
-push a (MinStack s1 s2@(S.Stack (x:xs))) =
+push a (MinStack s1 s2@(S.Stack (x:_))) =
   if a <= x
   then MinStack (S.push a s1) (S.push a s2)
   else MinStack (S.push a s1) s2
@@ -21,7 +21,7 @@ pop ms@(MinStack s1 s2) = case (S.peek s1, S.peek s2) of
   (Just a, Just b) -> if a > b 
                       then MinStack (S.pop s1) s2
                       else MinStack (S.pop s1) (S.pop s2)
-  otherwise -> ms
+  _                -> ms
 
 
 smin :: MinStack a -> Maybe a
diff --git a/src/chapter-3/Test/MinStack.hs b/src/chapter-3/Test/MinStack.hs
index 89dd9e9..2ae03a8 100644
--- a/src/chapter-3/Test/MinStack.hs
+++ b/src/chapter-3/Test/MinStack.hs
@@ -1,22 +1,22 @@
 module Test.MinStack where
 
-import Test.QuickCheck
 import Test.Hspec
 import Questions.MinStack
 import qualified Data.Stack as S
 
+exStack :: MinStack Int
 exStack = push 1 (push 7 (push 2 (push 6 (mkMinStack 9))))
 
 testMinStack :: SpecWith ()
 testMinStack = 
   describe "MinStack" $ do
-    describe "mkMinStack" $ do
-      it "should create a MinStack" $ do
-        (MinStack (S.mkStack 1) (S.mkStack 1) :: MinStack Int) `shouldBe` (mkMinStack 1)
-    describe "smin" $ do
-      it "should return the current min" $ do
+    describe "mkMinStack" $
+      it "should create a MinStack" $
+        (MinStack (S.mkStack 1) (S.mkStack 1) :: MinStack Int) `shouldBe` mkMinStack 1
+    describe "smin" $
+      it "should return the current min" $
         smin exStack `shouldBe` (Just 1 :: Maybe Int)
-    describe "push and pop" $ do
+    describe "push and pop" $
       it "should maintain min" $ do
         smin (push 0 exStack) `shouldBe` (Just 0 :: Maybe Int)
         smin (pop exStack) `shouldBe` (Just 2 :: Maybe Int)
diff --git a/src/chapter-3/Test/Queue.hs b/src/chapter-3/Test/Queue.hs
index 7c0e0c8..b72b8a0 100644
--- a/src/chapter-3/Test/Queue.hs
+++ b/src/chapter-3/Test/Queue.hs
@@ -1,6 +1,5 @@
 module Test.Queue where
 
-import Test.QuickCheck
 import Test.Hspec
 import Data.Queue
 
@@ -23,24 +22,24 @@ testQueue =
     it "should maintain FIFO order" $ do
       peek enqueueQueue `shouldBe` Just 1
       peek dequeueQueue `shouldBe` Just 3
-    describe "Eq instance" $ do
-      it "should maintain equality if regardless of enqueue/dequeue state" $ do
-        (Queue [1,2,3] [] == Queue [] [3,2,1]) `shouldBe` True
-    describe "mkQueue" $ do
-      it "should create a single element queue" $ do
-        mkQueue 1 `shouldBe` Queue [1] []
-    describe "enqueue" $ do
-      it "should add an element to the queue" $ do
-        enqueue 1 emptyQueue `shouldBe` Queue [1] []
-    describe "dequeue" $ do
-      it "should remove an element from the queue" $ do
+    describe "Eq instance" $
+      it "should maintain equality if regardless of enqueue/dequeue state" $
+        Queue [1,2,3] [] `shouldBe` (Queue [] [3,2,1] :: Queue Int)
+    describe "mkQueue" $
+      it "should create a single element queue" $
+        mkQueue 1 `shouldBe` (Queue [1] [] :: Queue Int)
+    describe "enqueue" $
+      it "should add an element to the queue" $
+        enqueue 1 emptyQueue `shouldBe` (Queue [1] [] :: Queue Int)
+    describe "dequeue" $
+      it "should remove an element from the queue" $
         dequeue exQueue `shouldBe` Queue [] [4,3,2,1]
     describe "peek" $ do
-      it "should return the next element in the queue if it exists" $ do
+      it "should return the next element in the queue if it exists" $
         peek exQueue `shouldBe` Just 5
-      it "should not crash on an empty queue" $ do
+      it "should not crash on an empty queue" $
         peek emptyQueue `shouldBe` (Nothing :: Maybe Int)
-    describe "isEmpty" $ do
+    describe "isEmpty" $
       it "should tell if a given queue is empty" $ do
         isEmpty emptyQueue `shouldBe` True
         isEmpty exQueue `shouldBe` False
diff --git a/src/chapter-3/Test/Stack.hs b/src/chapter-3/Test/Stack.hs
index a74e353..198975b 100644
--- a/src/chapter-3/Test/Stack.hs
+++ b/src/chapter-3/Test/Stack.hs
@@ -2,7 +2,6 @@ module Test.Stack where
 
 import Data.Stack
 import Test.Hspec
-import Test.QuickCheck
 import Data.Maybe (fromMaybe)
 
 exStack :: Stack Int
@@ -24,22 +23,22 @@ testStack =
       fromMaybe 0 (peek pushedStack)  `shouldBe` 1
       fromMaybe 0 (peek popedStack) `shouldBe` 3
 
-    describe "mkStack" $ do
-      it "should create a single element Stack" $ do
-        (mkStack 1) `shouldBe` (Stack [1])
-    describe "push" $ do
+    describe "mkStack" $
+      it "should create a single element Stack" $
+        mkStack 1 `shouldBe` (Stack [1] :: Stack Int)
+    describe "push" $
       it "should add an element to the stack" $ do
         push 0 exStack `shouldBe` Stack [0,1,2,3,4,5]
         push 1 emptyStack `shouldBe` mkStack 1
-    describe "pop" $ do
+    describe "pop" $
       it "should remove an element from the stack" $ do
-        pop exStack `shouldBe` (Stack [2,3,4,5])
+        pop exStack `shouldBe` Stack [2,3,4,5]
         pop emptyStack `shouldBe` emptyStack
-    describe "peek" $ do
+    describe "peek" $
       it "should return the first element in a stack" $ do
         peek exStack `shouldBe` Just 1
         peek (Stack []) `shouldBe` (Nothing :: Maybe Int)
-    describe "isEmpty" $ do
+    describe "isEmpty" $
       it "should tell if a given stack is empty" $ do
         isEmpty exStack `shouldBe` False
         isEmpty (Stack []) `shouldBe` True
diff --git a/test/Introduction/VI/Example01Spec.hs b/test/Introduction/VI/Example01Spec.hs
new file mode 100644
index 0000000..5594378
--- /dev/null
+++ b/test/Introduction/VI/Example01Spec.hs
@@ -0,0 +1,25 @@
+{-|
+Module      : Introduction.VI.Example01Spec
+Description : Introduction VI (Big O) Example 1 on Page 40---Tests
+-}
+module Introduction.VI.Example01Spec (main, spec) where
+
+import Prelude hiding (sum)
+
+import qualified Prelude as P (sum)
+
+import Test.Hspec (describe, hspec, Spec)
+import Test.Hspec.QuickCheck (prop)
+import Test.QuickCheck ((==>))
+import Test.QuickCheck.Modifiers (Positive (Positive))
+
+import Introduction.VI.Example01 hiding (main)
+
+main :: IO ()
+main = hspec spec
+
+spec :: Spec
+spec =
+  describe "properties" $
+    do prop "x <= 0 ==> sum x == 0" (\ x -> x <= 0 ==> sum x == 0)
+       prop "Posiitve x ==> sum x == Prelude.sum [1..x]" (\ (Positive x) -> sum x == P.sum [1..x])
diff --git a/test/Spec.hs b/test/Spec.hs
new file mode 100644
index 0000000..a824f8c
--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}