Add the haskell book

Haskell-book/03/.gitignore

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

Haskell-book/03/bower.json

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+{
+  "name": "03",
+  "ignore": [
+    "**/.*",
+    "node_modules",
+    "bower_components",
+    "output"
+  ],
+  "dependencies": {
+    "purescript-prelude": "^3.1.0",
+    "purescript-console": "^3.0.0",
+    "purescript-arrays": "^4.2.1",
+    "purescript-strings": "^3.3.1"
+  },
+  "devDependencies": {
+    "purescript-psci-support": "^3.0.0"
+  }
+}

Haskell-book/03/src/Main.purs

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+module Main where
+
+import Prelude
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (CONSOLE, log)
+import Data.String (singleton, drop, take)
+import Data.String.Unsafe (charAt)
+
+-- Given
+-- "Curry is awesome"
+-- Return
+-- "Curry is awesome!"
+a :: String -> String
+a x = x <> "!"
+
+-- Given
+-- "Curry is awesome!"
+-- Return
+-- "y"
+b :: String -> String
+b x = singleton $ charAt 4 x
+
+-- Given
+-- "Curry is awesome!"
+-- Return
+-- "awesome!"
+c :: String -> String
+c = drop 9
+
+-- If you apply your function to this value:
+-- "Curry is awesome"
+-- Your function should return
+-- 'r'
+thirdLetter :: String -> Char
+thirdLetter = charAt 2
+
+letterIndex :: Int -> Char
+letterIndex x = charAt x "Curry is awesome!"
+
+rvrs :: String -> String
+rvrs inp = (drop 9 inp) <> (drop 5 $ take 9 inp) <> (take 5 inp)
+
+main :: forall e. Eff (console :: CONSOLE | e) Unit
+main = do
+  log $ rvrs "Curry is awesome"

Haskell-book/03/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."