Add the haskell book

Haskell-book/04/.gitignore

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+/bower_components/
+/node_modules/
+/.pulp-cache/
+/output/
+/generated-docs/
+/.psc*
+/.purs*
+/.psa*

Haskell-book/04/bower.json

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+{
+  "name": "04",
+  "ignore": [
+    "**/.*",
+    "node_modules",
+    "bower_components",
+    "output"
+  ],
+  "dependencies": {
+    "purescript-prelude": "^3.1.0",
+    "purescript-console": "^3.0.0",
+    "purescript-tuples": "^4.1.0",
+    "purescript-lists": "^4.10.0",
+    "purescript-arrays": "^4.2.1",
+    "purescript-strings": "^3.3.1"
+  },
+  "devDependencies": {
+    "purescript-psci-support": "^3.0.0"
+  }
+}

Haskell-book/04/src/Ex.purs

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+module Ex where
+
+import Prelude
+import Data.Array (tail, reverse)
+import Data.Maybe (Maybe(..))
+import Data.String (toCharArray)
+import Data.Tuple (fst, snd, Tuple(..))
+
+awesome :: Array String
+awesome = ["Papuchon", "curry", ":)"]
+
+alsoAwesome :: Array String
+alsoAwesome = ["Quake", "The Simons"]
+
+allAwesome :: Array (Array String)
+allAwesome = [awesome, alsoAwesome]
+
+length :: forall a. Array a -> Int
+length n = length' 0 (tail n)
+    where length' i Nothing = i
+          length' i (Just k) = length' (i + 1) (tail k)
+
+isPalindrome :: String -> Boolean
+isPalindrome x = toCharArray x == reverse (toCharArray x)
+
+myAbs :: Int -> Int
+myAbs a = if a > 0 then a else -a
+
+f :: forall a b c d. Tuple a b -> Tuple c d -> Tuple (Tuple b d) (Tuple a c)
+f x y = Tuple (Tuple (snd x) (snd y)) (Tuple (fst x) (fst y))
+
+f' :: forall a b. (Tuple a b) -> a
+f' (Tuple a b) = a

Haskell-book/04/src/Main.purs

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+module Main where
+
+import Prelude
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (CONSOLE, log)
+
+main :: forall e. Eff (console :: CONSOLE | e) Unit
+main = do
+  log "Hello sailor!"

Haskell-book/04/test/Main.purs

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+module Test.Main where
+
+import Prelude
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (CONSOLE, log)
+
+main :: forall e. Eff (console :: CONSOLE | e) Unit
+main = do
+  log "You should add some tests."