haskell.gby

Size: px

Start display at page:

Download "haskell.gby"

たつぞうおえづか
7 years ago
Views:

1 Haskell 1

2 2

3 3

4 Haskell ( ) 4

5 Haskell Lisper 5

6 Haskell = Haskell 6

7 Haskell Haskell... 7

8 qsort [8,2,5,1] [1,2,5,8] "Hello, " ++ "world!" "Hello, world!" div 8 2 (+) div map even [1,2,3,4] [False,True,False,True] 8

9 not. even getline >>= putstrln 9

10 main = putstrln "Hello, world!" average x y = (x + y) / 2 if collatz n = if even n then n div 2 else n * subs [] = [[]] subs (x:xs) = yss ++ map (x:) yss where yss = subs xs odd = not. even -- odd n = not (even n) getputline = getline >>= putstrln 10

11 inp = getline; -- putstrln inp; ( ) getline >>= putstrln -- 11

12 12

13 C++ template <typename T> void qsort (T *result, T *list, int n) { if (n == 0) return; T *smallerlist, *largerlist; smallerlist = new T[n]; largerlist = new T[n]; T pivot = list[0]; int numsmaller=0, numlarger=0; for (int i = 1; i < n; i++) if (list[i] < pivot) smallerlist[numsmaller++] = list[i]; else largerlist[numlarger++] = list[i]; qsort(smallerlist,smallerlist,numsmaller); qsort(largerlist,largerlist,numlarger); int pos = 0; for ( int i = 0; i < numsmaller; i++) result[pos++] = smallerlist[i]; result[pos++] = pivot; for ( int i = 0; i < numlarger; i++) result[pos++] = largerlist[i]; delete [] smallerlist; delete [] largerlist; }; 13

14 Haskell qsort [] = [] qsort (p:ps) = qsort less ++ [p] ++ qsort more where less = filter (<p) ps more = filter (>=p) ps How what ( ) > qsort [8,2,5,1] [1,2,5,8] 14

15 15

16 Haskell x = x

17 17

18 (1) Perl for ($i=0; $i<10; $i++) { print "$i\n"; } mapm_ print [0..9] 18

19 (2) Perl $i = 0; while (<>) { $i++; } print "$i\n"; Haskell getcontents >>= print. length. lines 19

20 (3) Perl for ($i = 1; $i <= $n; $i++) { $ret = $ret * $i; } fact 1 = 1 fact n = n * fact (n-1) 20

21 21

22 (.) (>>=) Haskell 22

23 QuickCheck 23

24 Haskell QuickCheck prop_ordered xs = ordered (qsort xs) where ordered [] = True ordered [x] = True ordered (x:y:xs) = x <= y && ordered (y:xs) > quickcheck prop_ordered OK, passed 100 tests. 24

25 Haskell 25

26 PHP Ruby Lisp 型付け動的弱い強い極めて強い C Java Haskell 少ないコンパイラーが発見する間違い多い多くすべきテストの量少なくてもよい 26

27 Haskell 27

28 isdigit :: Char -> Bool a ) String [Char] (++) :: [a] -> [a] -> [a] a Int, Float, Double (+) :: (Num a) => a -> a -> a a Int, Char, String qsort :: Ord a => [a] -> [a] map :: (a -> b) -> [a] -> [b] IO getline :: IO String putstrln :: String -> IO () 28

29 if if then else then else collatz :: Int -> Int collatz n = if even n then n div 2 -- Int else n * Int 29

30 putstrln :: String -> IO () (++) :: [a] -> [a] -> [a] main = putstrln "Hello, " ++ "world!" main = (putstrln "Hello, ") ++ "world!" ++ (++) :: IO() -> [Char] -> [Char] main = putstrln ("Hello, " ++ "world!") 30

31 31

32 32

33 lines :: String -> [String] lines "" = [] lines s = let (l, s ) = break (== \n ) s in l : case s of [] -> [] (_:s ) -> lines s 33

34 data data Tree a = Leaf a Node (Tree a) (Tree a) data Bool = False True data Maybe a = Nothing Just a IO data IO a =... Haskell Maybe IO 34

35 Maybe On programming language design NULL C NULL, Java null, Python None, Lisp nil,... NULL NULL Haskell Maybe data Maybe a = Nothing Just a Just case mx of Nothing -> 0 Just x -> x + 1 maybe 0 (+1) mx 35

36 IO getline % cat a.hs main = getline >>= putstrln % runghc a.hs foo foo % runghc a.hs bar bar 36

37 IO IO IO IO main = getcontents >>= \inp -> putstrln (count inp) count :: String -> String count = show. length. lines IO IO IO getline :: IO String putstrln :: String -> IO () main :: IO () main = getline >>= putstrln IO ( ) 37

38 do do main = do -- :: IO () inp <- getline -- :: IO String putstrln inp -- :: String -> IO () main = getline >>= \inp -> putstrln inp main = getline >>= putstrln do 38

39 Haskell Haskell Simon PEYTON JONES 39

40 Parsec 40

41 Parsec 15 Perl6 Pugs Audrey Tang 41

42 vs BNF CSV 42

43 CSV ABNF RFC 4180 file = record *(CRLF record) [CRLF] record = field *(COMMA field) field = (escaped / non-escaped) escaped = DQUOTE *(TEXTDATA / COMMA / CR / LF / 2DQUOTE) DQUOTE non-escaped = *TEXTDATA TEXTDATA = %x20-21 / %x23-2b / %x2d-7e 43

44 sub parse_csv_line { my $text = shift; = (); while ($text =~ m/"([^"\\]*(\\.[^"\\]*)*)",? ([^,]+),?,/g) { push(@fields, defined($1)? $1 : defined($3)? $3 : ); } push(@fields, ) if $text =~ m/,$/; return \@fields; } while (<>) { chomp; my $ret = parse_csv_line($_); push(@csv, $ret); } 44

45 Parsec (1) file :: Parser [[String]] file = record sependby1 crlf record :: Parser [String] record = field sepby1 comma field :: Parser String field = escaped < > nonescaped escaped :: Parser String escaped = do dquote txt <- many (textdata < > comma < > cr < > lf < > try (dquote >> dquote)) dquote return txt nonescaped :: Parser String nonescaped = many textdata 45

46 Parsec (2) textdata :: Parser Char textdata = oneof ("!" ++ [ #.. + ] ++ [ -.. ~ ]) comma :: Parser Char comma = char, crlf :: Parser Char crlf = cr >> lf lf :: Parser Char lf = char \x0a cr :: Parser Char cr = char \x0d dquote :: Parser Char dquote = char " 46

47 Parser Parser dquote :: Parser Char many :: Parser a -> Parser [a] return :: a -> Parser a escaped :: Parser String escaped = do dquote txt <- many (textdata < > comma < > cr < > lf < > try (dquote >> dquote)) dquote return txt 47

48 file :: Parser [[String]] file = undefined record :: Parser [String] record = undefined field :: Parser String field = undefined 48

49 IO >>= 49

fp.gby

fp.gby 1 1 2 2 3 2 4 5 6 7 8 9 10 11 Haskell 12 13 Haskell 14 15 ( ) 16 ) 30 17 static 18 (IORef) 19 20 OK NG 21 Haskell (+) :: Num a => a -> a -> a sort :: Ord a => [a] -> [a] delete :: Eq a => a -> [a] -> [a]