1. Haskell programming language

2. Haskell is… Memory managed (allocation, collection) “Typeful” (static, strong) – Types are checked at compile-time – Types cannot be coerced (in general) Pure functional programming – Emphasis on functions – Referential transparency – All variables are constant

3. Haskell - pros & cons Concurrency – The #1 on Language Shootout for threading – All non-I/O code is concurrent by default – (mutations are handled as I/O code) Readability – No parentheses or commas – Higher-order functions reduce lines-of-code – (no syntax as a reminder of context)

4. Haskell - namespaces Main main True a Bool Eq -- modules (packages) -- value variables (functions) -- value constructors -- type variables (generics) -- type constructors -- type classes (interfaces)

5. Haskell - syntax Derived syntax f x = expr (x *) (* y) (*) x `times` y f $ g $ h x (f. g. h) x do a; b; c -- lambda -- sections -- infix func -- parens -- compose -- I/O bind Core syntax f = \x -> expr \y -> x * y \x -> x * y \x y -> x * y times x y f (g (h x)) a >>= b >>= c

6. Haskell - type syntax life = 42 :: Int life :: Int life = 42

7. Haskell - types “Hello” :: String length :: [a] -> Int floor :: Float -> Int map :: (a -> b) -> [a] -> [b] 42 :: Int (+) :: Int -> Int -> Int 42 :: Num a => a (+) :: Num a => a -> a -> a

8. Haskell - type system Int, Word, Float, Double, Char type String = [Char] data Maybe a = Nothing | Just a class Eq a where (==), (/=) :: a -> a -> Bool instance Eq Bool where True == True = True False == False = True _ == _ = False -- built-in types -- type synonyms -- data types -- type classes -- type class instances

9. Haskell - datatypes data Bool = False | True data Tree a = Leaf a | Branch (Tree a) (Tree a) data Rect = Rect Int Int Int Int data Rect = Rect { x, y :: Int, width :: Int, height :: Int} -- enumerations -- generics -- unlabeled record -- labeled record

10. Haskell - example programs main = return () main = putStrLn “Hello World” main = interact id main = interact (unlines. reverse. lines) main = do args <- getArgs case args of "-n":a -> putStr (unwords a) a -> putStrLn (unwords a) -- null program -- hello world -- UNIX cat -- GNU tac -- UNIX echo

11. version control system

12. Darcs - overview The Theory of Patches A “branch” is a set of patches “Spontaneous branches” Every checkout is a branch Every checkout is a repository

13. Darcs - interactive Interactive “pull” – You chose what patches to download Interactive “push” – You chose what patches to commit externally Interactive “record” – You chose what files to commit locally

14. Parsec parser library

15. Parsec - combinators many :: Parser a -> Parser [a] many1 :: Parser a -> Parser [a] optional :: Parser a -> Parser (Maybe a) sepBy :: Parser a -> Parser s -> Parser [a] sepBy1 :: Parser a -> Parser s -> Parser [a] endBy :: Parser a -> Parser s -> Parser [a] endBy1 :: Parser a -> Parser s -> Parser [a] char :: Char -> Parser Char between :: Parser open -> Parser close -> Parser a -> Parser a -- like regex* -- like regex+ -- like regex? --...,...,... --... ;... ;... ; -- c --

16. Parsec - example parsers number = many digit string = between (char ‘"’) (many anyChar) lisp = number string identifier parens $ many $ lexeme lisp

17. xmonad X11 window manager

18. XMonad - overview Tilling window manager (like Ratpoison) Libraries of extensions and status bars Customizable (config file is the app) Full keyboard accessibility

19. XMonad - example config module Main where import XMonad import System.Exit import qualified XMonad.StackSet as W import qualified Data.Map as M myKeys conf@(XConfig {XMonad.modMask = modMask}) = M.fromList $ [ ((modMask.|. shiftMask, xK_Return), spawn $ XMonad.terminal conf), ((modMask.|. shiftMask, xK_q ), io (exitWith ExitSuccess))] myMouseBindings (XConfig {XMonad.modMask = modMask}) = M.fromList $ [ ((modMask, button1), (\w -> focus w >> mouseMoveWindow w)), ((modMask, button2), (\w -> focus w >> windows W.swapMaster)), ((modMask, button3), (\w -> focus w >> mouseResizeWindow w))] defaults = defaultConfig { keys = myKeys, mouseBindings = myMouseBindings, terminal = "xterm"} main = xmonad defaults

20. Yi extensible text editor

21. Yi - overview Extensible – Fully dynamic application (hs-plugins) – All state is serialized and reloaded Customizable – yi --as=vim (for vim key bindings) – yi --as=emacs (for emacs key bindings)

22. Yi - structure Taken from

23. Haskell Thank You