Add remaining haskell book exercises

25 files changed, 873 insertions, 0 deletions

diff --git a/Haskell-book/14/addition/Addition.hs b/Haskell-book/14/addition/Addition.hs
new file mode 100644
index 0000000..474eecd
--- /dev/null
+++ b/Haskell-book/14/addition/Addition.hs
@@ -0,0 +1,35 @@
+module Addition where
+
+import Test.Hspec
+import Test.QuickCheck
+
+dividedBy :: Integral a => a -> a -> (a, a)
+dividedBy num denom = go num denom 0
+    where go n d count
+            | n < d = (count, n)
+            | otherwise =  go (n - d) d (count + 1)
+
+multiplyBy :: (Ord a, Eq a, Num a) => a -> a -> a
+multiplyBy a b
+    | a == 0 || b == 0 = 0
+    | a > 0 && b > 0   = multiplyBy' a b
+    | a < 0 && b < 0   = multiplyBy' (-a) (-b)
+    | a < 0 && b > 0   = -(multiplyBy' (-a) b)
+    | a > 0 && b < 0   = -(multiplyBy' a (-b))
+    where  multiplyBy' c 1 = c
+           multiplyBy' c d = c + (multiplyBy c (d - 1))
+
+main :: IO ()
+main = hspec $ do
+    describe "Addition" $ do
+        it "15 divided by 3 is 5" $ do
+            dividedBy 15 3 `shouldBe` (5, 0)
+        it "22 divided by 5 is 4 remainder 2" $ do
+            dividedBy 22 5 `shouldBe` (4, 2)
+        it "x + 1 is always greater than x" $ do
+            property $ \x -> x + 1 > (x :: Int)
+    describe "Multiplication" $ do
+        it "15 multiplied by 3 is 45" $ do
+            multiplyBy 15 3 `shouldBe` 45
+        it "22 multiplied by 5 is 110" $ do
+            multiplyBy 22 5 `shouldBe` 110
\ No newline at end of file
diff --git a/Haskell-book/14/addition/LICENSE b/Haskell-book/14/addition/LICENSE
new file mode 100644
index 0000000..6a042c2
--- /dev/null
+++ b/Haskell-book/14/addition/LICENSE
@@ -0,0 +1,30 @@
+Copyright Author name here (c) 2017
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Author name here nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\ No newline at end of file
diff --git a/Haskell-book/14/addition/README.md b/Haskell-book/14/addition/README.md
new file mode 100644
index 0000000..543097e
--- /dev/null
+++ b/Haskell-book/14/addition/README.md
@@ -0,0 +1 @@
+# addition
diff --git a/Haskell-book/14/addition/Setup.hs b/Haskell-book/14/addition/Setup.hs
new file mode 100644
index 0000000..9a994af
--- /dev/null
+++ b/Haskell-book/14/addition/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/Haskell-book/14/addition/addition.cabal b/Haskell-book/14/addition/addition.cabal
new file mode 100644
index 0000000..1dec256
--- /dev/null
+++ b/Haskell-book/14/addition/addition.cabal
@@ -0,0 +1,17 @@
+name:                addition
+version:             0.1.0.0
+license-file:        LICENSE
+author:              Chicken Little
+maintainer:          sky@isfalling.org
+category:            Text
+build-type:          Simple
+cabal-version:       >=1.10
+
+library
+  exposed-modules:     Addition
+  ghc-options:         -Wall -fwarn-tabs
+  build-depends:       base >= 4.7 && < 5
+                     , hspec
+                     , QuickCheck
+  hs-source-dirs:      .
+  default-language:    Haskell2010
diff --git a/Haskell-book/14/addition/stack.yaml b/Haskell-book/14/addition/stack.yaml
new file mode 100644
index 0000000..9e311c2
--- /dev/null
+++ b/Haskell-book/14/addition/stack.yaml
@@ -0,0 +1,66 @@
+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+# resolver:
+#  name: custom-snapshot
+#  location: "./custom-snapshot.yaml"
+resolver: lts-9.14
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#   extra-dep: true
+#  subdirs:
+#  - auto-update
+#  - wai
+#
+# A package marked 'extra-dep: true' will only be built if demanded by a
+# non-dependency (i.e. a user package), and its test suites and benchmarks
+# will not be run. This is useful for tweaking upstream packages.
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# (e.g., acme-missiles-0.3)
+extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+flags: {}
+
+# Extra package databases containing global packages
+extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.5"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor
\ No newline at end of file
diff --git a/Haskell-book/14/addition/stack.yaml.lock b/Haskell-book/14/addition/stack.yaml.lock
new file mode 100644
index 0000000..75bf3ab
--- /dev/null
+++ b/Haskell-book/14/addition/stack.yaml.lock
@@ -0,0 +1,12 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 9e880f85f76b7f35a2b6edd1af333ce7f7845d47e897c3509ddd18eaa2763779
+    size: 536352
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/9/14.yaml
+  original: lts-9.14
diff --git a/Haskell-book/14/morse/.gitignore b/Haskell-book/14/morse/.gitignore
new file mode 100644
index 0000000..cf4a5cf
--- /dev/null
+++ b/Haskell-book/14/morse/.gitignore
@@ -0,0 +1,3 @@
+.stack-work/
+morse.cabal
+*~
\ No newline at end of file
diff --git a/Haskell-book/14/morse/ChangeLog.md b/Haskell-book/14/morse/ChangeLog.md
new file mode 100644
index 0000000..1ae7856
--- /dev/null
+++ b/Haskell-book/14/morse/ChangeLog.md
@@ -0,0 +1,3 @@
+# Changelog for morse
+
+## Unreleased changes
diff --git a/Haskell-book/14/morse/LICENSE b/Haskell-book/14/morse/LICENSE
new file mode 100644
index 0000000..da7b69b
--- /dev/null
+++ b/Haskell-book/14/morse/LICENSE
@@ -0,0 +1,30 @@
+Copyright Author name here (c) 2017
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Author name here nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Haskell-book/14/morse/README.md b/Haskell-book/14/morse/README.md
new file mode 100644
index 0000000..8b8c638
--- /dev/null
+++ b/Haskell-book/14/morse/README.md
@@ -0,0 +1 @@
+# morse
diff --git a/Haskell-book/14/morse/Setup.hs b/Haskell-book/14/morse/Setup.hs
new file mode 100644
index 0000000..9a994af
--- /dev/null
+++ b/Haskell-book/14/morse/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/Haskell-book/14/morse/src/Main.hs b/Haskell-book/14/morse/src/Main.hs
new file mode 100644
index 0000000..1f73b90
--- /dev/null
+++ b/Haskell-book/14/morse/src/Main.hs
@@ -0,0 +1,59 @@
+module Main where
+
+import Control.Monad (forever, when)
+import Data.List (intercalate)
+import Data.Traversable (traverse)
+import Morse (stringToMorse, morseToChar)
+import System.Environment (getArgs)
+import System.Exit (exitFailure, exitSuccess)
+import System.IO (hGetLine, hIsEOF, stdin)
+
+convertToMorse :: IO ()
+convertToMorse = forever $ do
+    weAreDone <- hIsEOF stdin
+    when weAreDone exitSuccess
+
+    line <- hGetLine stdin
+    convertLine line
+
+    where convertLine line = do
+            let morse = stringToMorse line
+            case morse of
+                (Just str) -> putStrLn (intercalate " " str)
+                Nothing -> do
+                    putStrLn $ "ERROR: " ++ line
+                    exitFailure
+
+convertFromMorse :: IO ()
+convertFromMorse = forever $ do
+    weAreDone <- hIsEOF stdin
+    when weAreDone exitSuccess
+
+    line <- hGetLine stdin
+    convertLine line
+
+    where
+        convertLine line = do
+            let decoded :: Maybe String
+                decoded = traverse morseToChar (words line)
+
+            case decoded of
+                (Just s) -> putStrLn s
+                Nothing -> do
+                    putStrLn $ "ERROR: " ++ line
+                    exitFailure
+
+main :: IO ()
+main = do
+    mode <- getArgs
+    case mode of
+        [arg] ->
+            case arg of
+                "from" -> convertFromMorse
+                "to" -> convertToMorse
+                _ -> argError
+        _ -> argError
+
+    where argError = do
+            putStrLn "Please specify the first argument as being 'from' or 'to' morse, such as: morse to"
+            exitFailure
\ No newline at end of file
diff --git a/Haskell-book/14/morse/src/Morse.hs b/Haskell-book/14/morse/src/Morse.hs
new file mode 100644
index 0000000..03193e5
--- /dev/null
+++ b/Haskell-book/14/morse/src/Morse.hs
@@ -0,0 +1,68 @@
+module Morse
+       ( Morse
+       , charToMorse
+       , morseToChar
+       , stringToMorse
+       , letterToMorse
+       , morseToLetter
+       ) where
+
+import qualified Data.Map as M
+
+type Morse = String
+
+letterToMorse :: (M.Map Char Morse)
+letterToMorse = M.fromList [
+    ('a', ".-")
+  , ('b', "-...")
+  , ('c', "-.-.")
+  , ('d', "-..")
+  , ('e', ".")
+  , ('f', "..-.")
+  , ('g', "--.")
+  , ('h', "....")
+  , ('i', "..")
+  , ('j', ".---")
+  , ('k', "-.-")
+  , ('l', ".-..")
+  , ('m', "--")
+  , ('n', "-.")
+  , ('o', "---")
+  , ('p', ".--.")
+  , ('q', "--.-")
+  , ('r', ".-.")
+  , ('s', "...")
+  , ('t', "-")
+  , ('u', "..-")
+  , ('v', "...-")
+  , ('w', ".--")
+  , ('x', "-..-")
+  , ('y', "-.--")
+  , ('z', "--..")
+  , ('1', ".----")
+  , ('2', "..---")
+  , ('3', "...--")
+  , ('4', "....-")
+  , ('5', ".....")
+  , ('6', "-....")
+  , ('7', "--...")
+  , ('8', "---..")
+  , ('9', "----.")
+  , ('0', "-----")
+  ]
+
+morseToLetter :: M.Map Morse Char
+morseToLetter =
+    M.foldWithKey (flip M.insert) M.empty
+                  letterToMorse
+
+charToMorse :: Char -> Maybe Morse
+charToMorse c =
+    M.lookup c letterToMorse
+
+stringToMorse :: String -> Maybe [Morse]
+stringToMorse s =
+    sequence $ fmap charToMorse s
+
+morseToChar :: Morse -> Maybe Char
+morseToChar m = M.lookup m morseToLetter
\ No newline at end of file
diff --git a/Haskell-book/14/morse/src/WordNumber.hs b/Haskell-book/14/morse/src/WordNumber.hs
new file mode 100644
index 0000000..5b25ee2
--- /dev/null
+++ b/Haskell-book/14/morse/src/WordNumber.hs
@@ -0,0 +1,26 @@
+module WordNumber where
+
+import Data.List (unfoldr, intercalate)
+import Data.Maybe (Maybe(..))
+
+digitToWord :: Int -> String
+digitToWord 0 = "zero"
+digitToWord 1 = "one"
+digitToWord 2 = "two"
+digitToWord 3 = "three"
+digitToWord 4 = "four"
+digitToWord 5 = "five" 
+digitToWord 6 = "six"
+digitToWord 7 = "seven"
+digitToWord 8 = "eight"
+digitToWord 9 = "nine"
+digitToWord _ = ""
+
+digits :: Int -> [Int]
+digits n = reverse $ unfoldr unfold n
+    where unfold x
+                | x == 0    = Nothing
+                | otherwise = Just ((mod x 10), (div x 10))
+
+wordNumber :: Int -> String
+wordNumber n = intercalate "-" $ map digitToWord (digits n)
\ No newline at end of file
diff --git a/Haskell-book/14/morse/stack.yaml b/Haskell-book/14/morse/stack.yaml
new file mode 100644
index 0000000..22e3463
--- /dev/null
+++ b/Haskell-book/14/morse/stack.yaml
@@ -0,0 +1,66 @@
+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+# resolver:
+#  name: custom-snapshot
+#  location: "./custom-snapshot.yaml"
+resolver: lts-9.17
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#   extra-dep: true
+#  subdirs:
+#  - auto-update
+#  - wai
+#
+# A package marked 'extra-dep: true' will only be built if demanded by a
+# non-dependency (i.e. a user package), and its test suites and benchmarks
+# will not be run. This is useful for tweaking upstream packages.
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# (e.g., acme-missiles-0.3)
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.6"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor
\ No newline at end of file
diff --git a/Haskell-book/14/morse/stack.yaml.lock b/Haskell-book/14/morse/stack.yaml.lock
new file mode 100644
index 0000000..6ee2e72
--- /dev/null
+++ b/Haskell-book/14/morse/stack.yaml.lock
@@ -0,0 +1,12 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 82ff94eacdc32a857e5aec82268644fdc3d5bfca07692ceeeb97e2d8ce5726ef
+    size: 535915
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/9/17.yaml
+  original: lts-9.17
diff --git a/Haskell-book/14/morse/tests/CoArbitrary.hs b/Haskell-book/14/morse/tests/CoArbitrary.hs
new file mode 100644
index 0000000..dc0da3d
--- /dev/null
+++ b/Haskell-book/14/morse/tests/CoArbitrary.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+module CoArbitrary where
+
+import GHC.Generics
+import Test.QuickCheck
+
+data Bool' = True' | False' deriving (Generic)
+
+instance CoArbitrary Bool'
+
+trueGen :: Gen Int
+trueGen = coarbitrary True' arbitrary
+
+falseGen :: Gen Int
+falseGen = coarbitrary False' arbitrary
\ No newline at end of file
diff --git a/Haskell-book/14/morse/tests/WordNumberTest.hs b/Haskell-book/14/morse/tests/WordNumberTest.hs
new file mode 100644
index 0000000..d9623a9
--- /dev/null
+++ b/Haskell-book/14/morse/tests/WordNumberTest.hs
@@ -0,0 +1,24 @@
+module Main where
+
+import Test.Hspec
+import WordNumber (digitToWord, digits, wordNumber)
+
+main :: IO ()
+main = hspec $ do
+    describe "digitToWord" $ do
+        it "returns zero for 0" $ do
+            digitToWord 0 `shouldBe`"zero"
+        it "returns one for 1" $ do
+            digitToWord 1 `shouldBe` "one"
+
+    describe "digits" $ do
+        it "returns [1] for 1" $ do
+            digits 1 `shouldBe` [1]
+        it "returns [1, 0, 0] for 100" $ do
+            digits 100 `shouldBe` [1, 0, 0]
+
+    describe "wordNumber" $ do
+        it "one-zero-zero given 100" $ do
+            wordNumber 100 `shouldBe` "one-zero-zero"
+        it "nine-zero-zero-one for 9001" $ do
+            wordNumber 9001 `shouldBe` "nine-zero-zero-one"
\ No newline at end of file
diff --git a/Haskell-book/14/morse/tests/tests.hs b/Haskell-book/14/morse/tests/tests.hs
new file mode 100644
index 0000000..b27d3b3
--- /dev/null
+++ b/Haskell-book/14/morse/tests/tests.hs
@@ -0,0 +1,86 @@
+module Main where
+
+import qualified Data.Map as M
+import Morse
+import Test.QuickCheck
+import Test.QuickCheck.Gen (oneof)
+
+allowedChars :: [Char]
+allowedChars = M.keys letterToMorse
+
+allowedMorse :: [Morse]
+allowedMorse = M.elems letterToMorse
+
+charGen :: Gen Char
+charGen = elements allowedChars
+
+morseGen :: Gen Morse
+morseGen = elements allowedMorse
+
+prop_thereAndBackAgain :: Property
+prop_thereAndBackAgain =
+    forAll charGen (\c -> ((charToMorse c) >>= morseToChar) == Just c)
+
+main' :: IO ()
+main' = quickCheck prop_thereAndBackAgain
+
+data Trivial = Trivial deriving (Eq, Show)
+
+trivialGen :: Gen Trivial
+trivialGen = return Trivial
+
+instance Arbitrary Trivial where
+    arbitrary = trivialGen
+
+main :: IO ()
+main = do
+    sample trivialGen
+
+data Identity a = Identity a deriving (Eq, Show)
+
+identityGen :: Arbitrary a => Gen (Identity a)
+identityGen = do
+    a <- arbitrary
+    return (Identity a)
+
+instance Arbitrary a => Arbitrary (Identity a) where
+    arbitrary = identityGen
+
+identityGenInt :: Gen (Identity Int)
+identityGenInt = identityGen
+
+data Pair a b = Pair a b deriving (Eq, Show)
+
+pairGen :: (Arbitrary a, Arbitrary b) => Gen (Pair a b)
+pairGen = do
+    a <- arbitrary
+    b <- arbitrary
+    return (Pair a b)
+
+instance (Arbitrary a, Arbitrary b) => Arbitrary (Pair a b) where
+    arbitrary = pairGen
+
+pairGenIntString :: Gen (Pair Int String)
+pairGenIntString = pairGen
+
+data Sum a b = First a | Second b deriving (Eq, Show)
+
+sumGenEqual :: Gen (Sum Char Int)
+sumGenEqual = do
+    a <- arbitrary
+    b <- arbitrary
+    oneof [return $ First a,
+           return $ Second b]
+
+sumGenCharInt :: Gen (Sum Char Int)
+sumGenCharInt = sumGenEqual
+
+sumGenFirstPls :: (Arbitrary a, Arbitrary b) => Gen (Sum a b)
+sumGenFirstPls = do
+    a <- arbitrary
+    b <- arbitrary
+    frequency [(10, return $ First a),
+               (1, return $ Second b)]
+
+sumGenCharIntFirst :: Gen (Sum Char Int)
+sumGenCharIntFirst = sumGenFirstPls
\ No newline at end of file
diff --git a/Haskell-book/14/qc/qc.cabal b/Haskell-book/14/qc/qc.cabal
new file mode 100644
index 0000000..f0b5b3a
--- /dev/null
+++ b/Haskell-book/14/qc/qc.cabal
@@ -0,0 +1,32 @@
+name:           qc
+version:        0.1.0.0
+author:         Eugen Wissner
+maintainer:     belka@caraus.de
+category:       Math
+build-type:     Simple
+cabal-version:  >= 1.10
+
+library
+  hs-source-dirs: src
+  build-depends: base >= 4.7 && < 5
+               , QuickCheck
+  exposed-modules: UsingQuickCheck
+  ghc-options: -Wall
+  default-language: Haskell2010
+
+test-suite tests
+  type: exitcode-stdio-1.0
+  main-is: UsingQuickCheckTest.hs
+  hs-source-dirs: tests
+  ghc-options: -Wall
+  build-depends: base >= 4.7 && < 5
+               , QuickCheck
+               , qc
+
+test-suite idempotence
+  type: exitcode-stdio-1.0
+  main-is: Idempotence.hs
+  hs-source-dirs: tests
+  ghc-options: -Wall
+  build-depends: base >= 4.7 && < 5
+               , QuickCheck
\ No newline at end of file
diff --git a/Haskell-book/14/qc/src/UsingQuickCheck.hs b/Haskell-book/14/qc/src/UsingQuickCheck.hs
new file mode 100644
index 0000000..f0fa27f
--- /dev/null
+++ b/Haskell-book/14/qc/src/UsingQuickCheck.hs
@@ -0,0 +1,58 @@
+module UsingQuickCheck where
+
+import Test.QuickCheck
+
+--
+-- 1
+--
+half :: (Eq a, Fractional a) => a -> a
+half x = x / 2
+
+halfIdentity :: (Eq a, Fractional a) => a -> a
+halfIdentity = (*2) . half
+
+--
+-- 2
+--
+-- for any list you apply sort to
+-- this property should hold
+listOrdered :: (Ord a) => [a] -> Bool
+listOrdered xs =
+    snd $ foldr go (Nothing, True) xs
+    where go _ status@(_, False) = status
+          go y (Nothing, t) = (Just y, t)
+          go y (Just x, _) = (Just y, x >= y)
+
+--
+-- 3
+--
+plusAssociative :: (Ord a, Integral a) => a -> a -> a -> Bool
+plusAssociative x y z = x + (y + z) == (x + y) + z
+
+plusCommutative :: (Ord a, Integral a) => a -> a -> Bool
+plusCommutative x y = x + y == y + x
+
+--
+-- 4
+--
+mulAssociative :: (Ord a, Integral a) => a -> a -> a -> Bool
+mulAssociative x y z = x * (y * z) == (x * y) * z
+
+mulCommutative :: (Ord a, Integral a) => a -> a -> Bool
+mulCommutative x y = x * y == y * x
+
+data Fool = Fulse
+          | Frue
+          deriving (Eq, Show)
+
+data Fool' = Fulse' -- 2/3
+           | Frue'  -- 1/3
+           deriving (Eq, Show)
+
+instance Arbitrary Fool where
+    arbitrary = oneof [ return Fulse
+                      , return Frue ]
+
+instance Arbitrary Fool' where
+    arbitrary = frequency [ (3, return Fulse')
+                          , (1, return Frue')]
\ No newline at end of file
diff --git a/Haskell-book/14/qc/stack.yaml b/Haskell-book/14/qc/stack.yaml
new file mode 100644
index 0000000..22e3463
--- /dev/null
+++ b/Haskell-book/14/qc/stack.yaml
@@ -0,0 +1,66 @@
+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+# resolver:
+#  name: custom-snapshot
+#  location: "./custom-snapshot.yaml"
+resolver: lts-9.17
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#   extra-dep: true
+#  subdirs:
+#  - auto-update
+#  - wai
+#
+# A package marked 'extra-dep: true' will only be built if demanded by a
+# non-dependency (i.e. a user package), and its test suites and benchmarks
+# will not be run. This is useful for tweaking upstream packages.
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# (e.g., acme-missiles-0.3)
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.6"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor
\ No newline at end of file
diff --git a/Haskell-book/14/qc/tests/Idempotence.hs b/Haskell-book/14/qc/tests/Idempotence.hs
new file mode 100644
index 0000000..4b484d0
--- /dev/null
+++ b/Haskell-book/14/qc/tests/Idempotence.hs
@@ -0,0 +1,30 @@
+module Main where
+
+import Data.Char
+import Data.List
+import Test.QuickCheck
+
+capitalizeWord :: String -> String
+capitalizeWord [] = []
+capitalizeWord (x:xs) = toUpper x : xs
+
+twice :: (a -> a) -> (a -> a)
+twice y = y . y
+
+fourTimes :: (a -> a) -> (a -> a)
+fourTimes = twice . twice
+
+f :: String -> Bool
+f x = 
+    (capitalizeWord x == twice capitalizeWord x)
+    && (capitalizeWord x == fourTimes capitalizeWord x)
+
+f' :: Ord a => [a] -> Bool
+f' x =
+    (sort x == twice sort x)
+    && (sort x == fourTimes sort x)
+
+main :: IO ()
+main = do
+    quickCheck f
+    quickCheck (f' :: String -> Bool)
\ No newline at end of file
diff --git a/Haskell-book/14/qc/tests/UsingQuickCheckTest.hs b/Haskell-book/14/qc/tests/UsingQuickCheckTest.hs
new file mode 100644
index 0000000..da5ddb5
--- /dev/null
+++ b/Haskell-book/14/qc/tests/UsingQuickCheckTest.hs
@@ -0,0 +1,128 @@
+module Main where
+
+import Data.List (sort)
+import UsingQuickCheck
+import Test.QuickCheck
+
+prop_half :: (Eq a, Fractional a) => a -> Bool
+prop_half x = (halfIdentity x) == x
+
+associativeGen :: (Integer -> Integer -> Integer -> Bool) -> Gen Bool
+associativeGen f = do
+    x <- (arbitrary :: Gen Integer)
+    y <- (arbitrary :: Gen Integer)
+    z <- (arbitrary :: Gen Integer)
+    elements [f x y z]
+
+commutativeGen :: (Integer -> Integer -> Bool) -> Gen Bool
+commutativeGen f = do
+    x <- (arbitrary :: Gen Integer)
+    y <- (arbitrary :: Gen Integer)
+    elements [f x y]
+
+assocNotNegGen :: (Int -> Int -> Int -> Bool) -> Gen Bool
+assocNotNegGen f = do
+    x <- choose (1 :: Int, 100)
+    y <- choose (1 :: Int, 100)
+    z <- choose (1 :: Int, 100)
+    elements [f x y z]
+
+commutNotNegGen :: (Int -> Int -> Bool) -> Gen Bool
+commutNotNegGen f = do
+    x <- choose (1 :: Int, 100)
+    y <- choose (1 :: Int, 100)
+    elements [f x y]
+    
+
+prop_quotRem :: Property
+prop_quotRem =
+    forAll (prop_quotRem') (\(x ,y) -> (quot x y) * y + (rem x y) == x)
+    where prop_quotRem' = do
+          x <- choose (1 :: Int, 10000)
+          y <- choose (1 :: Int, 10000)
+          return (x, y)
+
+prop_divMod :: Property
+prop_divMod =
+    forAll (prop_divMod') (\(x ,y) -> (div x y) * y + (mod x y) == x)
+    where prop_divMod' = do
+          x <- choose (1 :: Int, 10000)
+          y <- choose (1 :: Int, 10000)
+          return (x, y)
+
+prop_reverse :: Property
+prop_reverse =
+    forAll prop_reverse' (\xs -> (reverse . reverse) xs == id xs)
+    where prop_reverse' = do
+          x <- (arbitrary :: Gen [Integer])
+          return x
+
+prop_dollar :: Property
+prop_dollar =
+    forAll prop_dollar' (\x -> x)
+    where prop_dollar' = do
+          x <- (arbitrary :: Gen Integer)
+          return ((id $ x) == (id x))
+
+prop_point :: Property
+prop_point =
+    forAll prop_point' (\x -> x)
+    where prop_point' = do
+          x <- (arbitrary :: Gen Integer)
+          let pointFunc = negate . id
+          let appliedFunc = \y -> negate (id y)
+          return (pointFunc x == appliedFunc x)
+
+prop_foldr1 :: Property
+prop_foldr1 =
+    forAll prop_foldr1' (\x -> x)
+    where prop_foldr1' = do
+          x <- (arbitrary :: Gen [Integer])
+          y <- (arbitrary :: Gen [Integer])
+          return ((foldr (:) x y) == (x ++ y))
+
+prop_foldr2 :: Property
+prop_foldr2 =
+    forAll prop_foldr2' (\x -> x)
+    where prop_foldr2' = do
+          x <- (arbitrary :: Gen [[Integer]])
+          return ((foldr (++) [] x) == (concat x))
+
+prop_length :: Property
+prop_length =
+    forAll prop_length' (\x -> x)
+    where prop_length' = do
+          n <- (arbitrary :: Gen Int)
+          xs <- (arbitrary :: Gen [Integer])
+          return ((length (take n xs)) == n)
+
+prop_readShow :: Property
+prop_readShow =
+    forAll prop_readShow' (\x -> x)
+    where prop_readShow' = do
+          x <- (arbitrary :: Gen Integer)
+          return ((read (show x)) == x)
+
+main :: IO ()
+main = do
+    quickCheck (prop_half :: Double -> Bool)
+    quickCheck $ (listOrdered :: [Int] -> Bool) . sort
+    
+    quickCheck $ associativeGen plusAssociative
+    quickCheck $ commutativeGen plusCommutative
+    quickCheck $ associativeGen mulAssociative
+    quickCheck $ commutativeGen mulCommutative
+
+    quickCheck prop_quotRem
+    quickCheck prop_divMod
+
+    quickCheck $ assocNotNegGen (\x y z -> x ^ (y ^ z) == (x ^ y) ^ z)
+    quickCheck $ commutNotNegGen (\x y -> x ^ y == y ^ x)
+
+    quickCheck prop_reverse
+    quickCheck prop_dollar
+    quickCheck prop_point
+    quickCheck prop_foldr1
+    quickCheck prop_foldr2
+    quickCheck prop_length
+    quickCheck prop_readShow
\ No newline at end of file