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
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
-- lambda
-- sections
-- infix func
-- parens
-- compose
-- I/O bind

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 -- enumerations -- generics -- unlabeled record
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]
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 {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. extensible text editorYi
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