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Haskell语言的概览性介绍,内容有: 若干语言特性(是什么让Haskell如此独特?):Lambda,Curry, Algebraic Data Type,Type Class, Purity,Lazy Evaluation; 对并行与并发的支持; 若干有启发性的例子以及性能问题; Haskell在工业界的应用;

TRANSCRIPT

  • 1.Hi Haskell

2.

  • A language that doesnt effect how you think about programming is not worth learning

Alan Perlis 3.

  • Haskell
    • Lambda Curry
    • Algebraic Data Type Type Class
    • Purity, Lazy Evaluation
  • (optional)
  • Haskell

4. (Programming Paradigm)

  • --

5.

  • Imperative
  • Declarative
  • Object-Oriented
  • Aspect-Oriented
  • Event-Driven
  • Functional
  • Generic
  • Logic
  • Concurrent

6. 7. Functional Programming

  • FP (evaluation) (mutable) FP (application)

8.

  • ,Haskell
  • pure )
  • FP

9. Lambda

  • (x y->x*10+y) 5 9
  • --59
  • //JavaScript
  • (function (x,y){
  • return x*10 + y
  • })(5,9)

10. First-Class Function & High Order Function

  • Int Float

11. Currying(Partial Application)&High Order

  • -- f::Int->Int->Int
  • -- f::Int->(Int->Int)
  • f x y=x*10 + y
  • f5 = f 5
  • f7 = f 7
  • f5 9 -- 59
  • f5 1 -- 51
  • f7 9 -- 79
  • f7 1 -- 71
  • //JavaScript
  • function f(x) {
  • return function(y) {
  • return x * 10 + y
  • }
  • }
  • f5 = f(5)
  • f7 = f(7)
  • f5(9) // 59
  • f7(1) // 71

12. - 3D

  • (R,R) -> (R,R,R)
  • (R,R,R) -> R,
  • (R,R) -> R
  • 2D : R -> (R,R)
  • : (R,R,R) -> (R,R,R)
  • : (R,R) -> Color

13. Example -FieldTrip http://www.haskell.org/haskellwiki/FieldTrip

  • talk is cheap
  • show me the running code

14. Example -FieldTrip

  • circle :: Curve2
  • semiCircle :: Curve2
  • -- Z
  • revolve :: Curve2 -> ParamSurf
  • torus :: R -> R -> ParamSurf
  • -- sr cr:
  • torus sr cr = revolve (const (sr,0) ^+^ const cr *^ circle)
  • sphere = revolve semiCircle

15. Example - 3D

  • 3D

16. Algebraic Data Type

  • data
  • constructor
  • constructor
  • data Maybe a =
  • Just a
  • | Nothing
  • data Tree a =
  • Empty
  • | Leaf a
  • | Node(Tree a)(Tree a)

Constructor Constructor 17. Algebraic Data Type

  • Maybe Maybe Int
    • Just 20
    • Nothing
  • Maybe Int

18. Pattern Matching

  • constructor
  • pattern
  • tree =
  • Node (Leaf 4) (Node Empty (Leaf 5))
  • accum Empty = 0
  • accum (Leaf a) = a
  • accum (Node left right) = (accum left) + (accum right)
  • accum tree -- 9

19.

  • list

20. Type Classes

  • classEq a where
  • (==) :: a -> a -> Bool
  • elem :: Eq a => a->[a]->Bool
  • elem k (x:xs)
  • | k == x = True
  • | otherwise = elem k xs
  • elem k [] = False

OO class 21. Instance of Type Classes

  • instanceEq (Maybe a) where
  • Just v1 == Just v2 = v1 == v2
  • Nothing == Nothing = True
  • _ == _= False

22. Lazy Evaluation

  • a = [1..] -- infinite list
  • take 3 a -- [1,2,3]

23. Purity

  • Functional

24. Purity

  • variable
  • a = 3
  • a = 19

25. Purity

  • side effect

26. Referential Transparent

  • 2 * f(x) f(x) + f(x)
  • int y = 10;
  • int f(int i)
  • {
  • return i + y++;
  • }
  • f(5) + f(5); // 15 + 16 = 31
  • 2 * f(5);// 2 * 15 = 30

27.

28. IO Action

  • IO () IO first-class IO IO main IO
  • IO
  • IO main

--putStrLn :: String -> IO () --main :: IO () main = putStrLn "Hi Haskell!" 29. Monad

  • IO Action Monad
  • Monster
  • Haskell Monad Monad "warm fuzzy thing" ( )!
    • --Simon Peyton Jones Haskell

30. Monad

  • class Monad m where
  • bind:: m a -> (a -> m b) -> m b
  • inject:: a ->m a

Monad m a bind inject a (a -> m b) 31. Example -

  • DSL
  • Haskell EDSL
    • Algebraic Data Type

32. Example - , Hommage Haskell Offline Music Manipulation And Generation EDSL http://substitut-fuer-feinmotorik.net/projects/haskellommage 33.

34.

  • forkIO :: IO () -> IO ThreadId
  • forkIO (writeFile "temp.txt" "haskell thread")

35. Shared Mutable State Concurrency

  • Race conditions due to forgotten locks
  • Deadlocks resulting from inconsistent lock ordering
  • Corruption caused by uncaught exceptions
  • Lost wakeups induced by omitted notifications

36. Software Transactional Memory(STM)

  • transaction
  • a b
    • transaction
    • transaction

37. STM Sample

  • import Control.Concurrent.STM
  • type Bal =TVarFloat
  • transfer::Float->Bal->Bal->STM ()
  • transfer qty fromBal toBal = do
  • fromQty STM a
  • catchSTM :: STM a -> (exception->STM a) -> STM a
  • instance Monad STM
  • complexAction = action1 `orElse` action2
  • main = atomically complexAction

40.

  • --
  • sort :: (Ord a) => [a] -> [a]
  • sort (x:xs) = lesser ++ x:greater
  • where lesser = sort [y | y [a] -> [a]
  • parSort (x:xs) =forcegreater`par`
  • ( forcelesser`pseq`(lesser ++ x:greater))
  • where lesser = parSort [y | y (a -> b) -- map function
  • -> Strategy c -- evaluation strategy for reduction
  • -> ([b] -> c) -- reduce function
  • -> [a] -- list to map over
  • -> c
  • mapReduce mapStrat mapFunc reduceStrat reduceFunc input
  • = mapResult `pseq` reduceResult
  • where mapResult = parMap mapStrat mapFunc input
  • reduceResult = reduceFunc mapResult `using` reduceStrat

45.

  • GPU
  • CPU
  • GPU Shader CUDA OpenCL
  • GPU FP
  • GPipe EDSL GPU , Haskell GPU Haskell OpenGL GLSL

46. Example - GPU

  • GPipe
  • http://www.haskell.org/haskellwiki/GPipe

47. Parser Combinator

  • parse
  • parse
  • ( Lex Yacc Flex Bison Antlr) parse
  • Haskell parser Parser Combinator

48. Example - Parser Combinator for JavaScript

  • parser :String -> Result
  • Result 3
    • remaining: parse
    • matched: parser parse
    • ast: parse
  • parser
    • range("0", "9")
    • token("begin")
  • parser combinator ( )parser
    • repeat1(alternate(sequence(parser1, parser2), parser3))

49. EDSL

  • first-class
  • combinator

50.

  • --
  • TheComputerLanguageBenchmarksGame
    • http://shootout.alioth.debian.org/
    • Haskell C 1/5
  • 2D
    • http://blog.csdn.net/soloist/archive/2009/04/09/4060081.aspx

51. 52. 53.

  • Haskell
  • FP Scala Haskell Java JVM
  • FP Haskell FP programmer

54.

  • [email_address]
  • http://blog.csdn.net/soloist
  • FP

55.