Added Chapter 3

Ch03/Code01_base1/Code0301.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0301.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0301
+version:             0.1.0.0
+synopsis:            Display a number in another base.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0301
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code01_base1/Main.hs

@@ -0,0 +1,17 @@
+import Data.Char (intToDigit, chr, ord) 
+import Numeric (showIntAtBase)
+
+-- Converts a number n to the base b
+n `inBase` b = showIntAtBase b numToLetter n ""
+
+numToLetter :: Int -> Char
+numToLetter n
+  | n < 10 = intToDigit n
+  | otherwise = chr (ord 'a' + n - 10)
+
+main :: IO ()
+main = do
+  putStrLn $ 8 `inBase` 12
+  putStrLn $ 10 `inBase` 12
+  putStrLn $ 12 `inBase` 12
+  putStrLn $ 47 `inBase` 12

Ch03/Code01_base1/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0301 *~ 

Ch03/Code02_base2/Code0302.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0302.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0302
+version:             0.1.0.0
+synopsis:            Reading a number from another base.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0302
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code02_base2/Main.hs

@@ -0,0 +1,20 @@
+import Data.Char (ord, digitToInt, isDigit)
+import Numeric (readInt)
+
+main :: IO ()
+main = do
+  print $ "8" `base` 12
+  print $ "a" `base` 12
+  print $ "10" `base` 12
+  print $ "3b" `base` 12
+
+-- Decodes a number from base b  
+str `base` b = readInt b isValidDigit letterToNum str
+
+letterToNum :: Char -> Int
+letterToNum d
+  | isDigit d = digitToInt d
+  | otherwise = ord d - ord 'a' + 10
+                
+isValidDigit :: Char -> Bool
+isValidDigit d = letterToNum d >= 0

Ch03/Code02_base2/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0302 *~ 

Ch03/Code03_substring/Code0303.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0303.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0303
+version:             0.1.0.0
+synopsis:            Searching for a string.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0303
+  main-is:             Main.hs
+  -- other-modules:       
+  other-extensions:    OverloadedStrings
+  build-depends:       base >=4.6 && <4.7, bytestring >=0.10 && <0.11
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code03_substring/Main.hs

@@ -0,0 +1,12 @@
+import Data.ByteString (breakSubstring)
+import qualified Data.ByteString.Char8 as C
+
+main = do
+  print $ substringFound "scraf" "swedish scraf mafia"
+  print $ substringFound "flute" "swedish scraf mafia"
+
+-- Finds a substring from a query
+substringFound :: String -> String -> Bool  
+substringFound query str = (not . C.null . snd) $ 
+                           breakSubstring (C.pack query) (C.pack str)
+                           

Ch03/Code03_substring/Main2.hs

@@ -0,0 +1,7 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.ByteString (isInfixOf)
+
+main = do
+  print $ isInfixOf "scraf" "swedish scraf mafia"
+  print $ isInfixOf "flute" "swedish scraf mafia"

Ch03/Code03_substring/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0303 *~ 

Ch03/Code04_bm/Code0304.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0304.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0304
+version:             0.1.0.0
+synopsis:            Performing the Boyer–Moore–Horspool string search.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0304
+  main-is:             Main.hs
+  -- other-modules:       
+  other-extensions:    OverloadedStrings
+  build-depends:       base >=4.6 && <4.7, stringsearch >=0.3 && <0.4, bytestring >=0.10 && <0.11, deepseq >=1.3 && <1.4, containers >=0.5 && <0.6
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code04_bm/Main.hs

@@ -0,0 +1,29 @@
+import Data.Map (fromList, (!), findWithDefault)
+
+indexMap xs = fromList $ zip [0..] xs
+revIndexMap xs = fromList $ zip (reverse xs) [0..]
+
+-- Runs the Boyer–Moore–Horspool substring search algorithm
+bmh :: Ord a => [a] -> [a] -> Maybe Int
+bmh pat xs = bmh' (length pat - 1) (reverse pat) xs pat
+
+bmh' :: Ord a => Int -> [a] -> [a] -> [a] -> Maybe Int
+bmh' n [] xs pat = Just (n + 1)
+bmh' n (p:ps) xs pat 
+  | n >= length xs = Nothing
+  | p == (indexMap xs) ! n = bmh' (n - 1) ps xs pat
+  | otherwise  = bmh' (n + findWithDefault (length pat) 
+                       (sMap ! n) pMap) (reverse pat) xs pat
+  where sMap = indexMap xs
+        pMap = revIndexMap pat
+
+main :: IO ()
+main = do
+  let corpus = "hello world!"
+  print $ bmh "ello" corpus
+  print $ bmh "wor" corpus
+  print $ bmh "xyz" corpus
+  print $ bmh "abc" corpus
+  print $ bmh "ld" corpus
+  print $ bmh "world" corpus
+

Ch03/Code04_bm/Main2.hs

@@ -0,0 +1,29 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.ByteString.Search (indices)
+import qualified Data.ByteString as BS
+import Control.DeepSeq
+
+main = do
+  corpus <- BS.readFile "big.txt"
+  print $ map (\x -> (not.null) (indices x corpus)) shortNeedles 
+
+
+shortNeedles = [ "abc", "fwi", "lqa", "pwf", "ooo"
+               , "mos", "fez", "cwd", "qfo", "mic"
+               , "zoe", "qdk", "bbc", "wwi", "qad"
+               , "fwf", "sos", "zez", "dwd", "ofo"
+               , "cic", "zde", "kdq", "bna", "uin"]
+
+longNeedles = ["immobilisation", "Your excellency!", "were times when militiamen"
+              ,"haskell b curry", "rode silently on his small gray horse"
+              , "In regard to philanthropy", "computers are cool", "degree we may imagine"
+              , "definitely not", "Only by reducing this element"
+              , "imnobilisation", "Ydur excellency!", "were times xhen militiamen"
+              ,"With your permission", "rode silentxly on his small gray horse"
+              , "exclaimed Natasha.", "During the third night the countess kept", "degfree we may imagine"
+              , "definiteldy not", "Only by reducingthis element" ] 
+
+
+
+

Ch03/Code04_bm/Makefile

@@ -0,0 +1,6 @@
+default:
+	wget -N norvig.com/big.txt
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0304 big.txt *~ 

Ch03/Code05_rk/Code0305.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0305.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0305
+version:             0.1.0.0
+synopsis:            Performing the Rabin-Karp string search.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0305
+  main-is:             Main.hs
+  -- other-modules:       
+  other-extensions:    OverloadedStrings
+  build-depends:       base >=4.6 && <4.7, stringsearch >=0.3 && <0.4, bytestring >=0.10 && <0.11, deepseq >=1.3 && <1.4, containers >=0.5 && <0.6
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code05_rk/Main.hs

@@ -0,0 +1,11 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.ByteString.Search.KarpRabin (indicesOfAny)
+import qualified Data.ByteString as BS
+
+-- Finds substrings
+main = do
+  let needles = [ "preparing to go away"
+                , "is some letter of recommendation"]
+  haystack <- BS.readFile "big.txt"
+  print $ indicesOfAny needles haystack

Ch03/Code05_rk/Makefile

@@ -0,0 +1,6 @@
+default:
+	wget -N norvig.com/big.txt
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0305 big.txt *~ 

Ch03/Code06_split/Code0306.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0306.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0306
+version:             0.1.0.0
+synopsis:            Splitting a string.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0306
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7, split >=0.2 && <0.3
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code06_split/Main.hs

@@ -0,0 +1,17 @@
+import Data.List.Split (splitOn)
+
+-- Splits a string by some delimeter
+main = do 
+  input <- readFile "input.txt"
+  let ls = lines input
+  print $ ls
+  -- ["first line","second line","words are split by space","comma,separated,values","or any delimiter you want"]
+  let ws = words $ ls !! 2
+  print ws
+  -- ["words","are","split","by","space"]
+  let cs = splitOn "," $ ls !! 3
+  print cs
+  -- ["comma","separated","values"]
+  let ds = splitOn "an" $ ls !! 4
+  print ds
+  -- ["or any d","limit","r you want"]

Ch03/Code06_split/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0306 *~ 

Ch03/Code06_split/input.txt

@@ -0,0 +1,5 @@
+first line
+second line
+words are split by space
+comma,separated,values
+or any delimiter you want

Ch03/Code07_lcs/Code0307.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0307.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0307
+version:             0.1.0.0
+synopsis:            Longest common subsequence calculation.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0307
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7, data-memocombinators >=0.5 && <0.6
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code07_lcs/Main.hs

@@ -0,0 +1,23 @@
+import qualified Data.MemoCombinators as Memo
+
+memoize :: (String -> String -> r) -> String -> String -> r
+memoize = Memo.memo2 (Memo.list Memo.char) (Memo.list Memo.char)
+
+-- Finds the longest common subsequence
+lcs :: String -> String -> String
+lcs = memoize lcs'
+  where lcs' xs'@(x:xs) ys'@(y:ys)
+          | x == y    = x : lcs xs ys
+          | otherwise = longer (lcs xs' ys) (lcs xs ys')
+        lcs' _ _ = []
+        longer as bs
+          | length as > length bs = as
+          | otherwise = bs
+
+
+main :: IO ()
+main = do
+  let xs = "find the lights"
+  let ys = "there are four lights"
+  print $ lcs xs ys
+  

Ch03/Code07_lcs/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0307 *~ 

Ch03/Code08_phon/Code0308.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0308.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0308
+version:             0.1.0.0
+synopsis:            Calculating phonetic codes.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0308
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7, phonetic-code >=0.1 && <0.2
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code08_phon/Main.hs

@@ -0,0 +1,12 @@
+import Text.PhoneticCode.Soundex (soundexNARA, soundexSimple)
+import Text.PhoneticCode.Phonix (phonix)
+
+ws = ["haskell", "hackle", "haggle", "hassle"]
+
+-- Computes the phonetic codes
+main :: IO ()
+main = do
+  print $ map soundexNARA ws
+  print $ map soundexSimple ws
+  print $ map phonix ws
+  

Ch03/Code08_phon/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0308 *~ 

Ch03/Code09_edit/Code0309.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0309.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0309
+version:             0.1.0.0
+synopsis:            Calculating edit distance.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0309
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7, data-memocombinators >=0.5 && <0.6
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code09_edit/Main.hs

@@ -0,0 +1,22 @@
+import qualified Data.MemoCombinators as Memo
+
+main = do
+  print $ lev "mercury" "sylvester"
+
+-- Computes the edit distance  
+lev :: Eq a => [a] -> [a] -> Int
+lev a b = levM (length a) (length b)
+  where levM = memoize lev'
+        lev' i j
+          | min i j == 0 = max i j
+          | otherwise    = minimum 
+                           [ ( 1 + levM (i-1) j )
+                           , ( 1 + levM i (j-1) )
+                           , ( ind i j + levM (i-1) (j-1) ) ]
+        ind i j
+          | a !! (i-1) == b !! (j-1) = 0
+          | otherwise                = 1
+    
+min3 a b c = min (min a b) c
+
+memoize = Memo.memo2 (Memo.integral) (Memo.integral)

Ch03/Code09_edit/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0309 *~ 

Ch03/Code10_jw/Code0310.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0310.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0310
+version:             0.1.0.0
+synopsis:            Calculating Jaro–Winkler distance.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0310
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code10_jw/Main.hs

@@ -0,0 +1,30 @@
+import Data.List (elemIndices)
+
+main = do
+  print $ jaro "marisa" "magical"
+  print $ jaro "haskell" "hackage"
+
+-- Computes the Jaro-Winkler distance  
+jaro :: Eq a => [a] -> [a] -> Double
+jaro s1 s2
+  | m == 0    = 0.0
+  | otherwise = (1/3) * (m/ls1 + m/ls2 + (m-t)/m)
+  where ls1 = toDouble $ length s1
+        ls2 = toDouble $ length s2
+        m' = matching s1 s2 d
+        d = fromIntegral $ max (length s1) (length s2) `div` 2 - 1
+        m = toDouble m'
+        t = toDouble $ (m' - matching s1 s2 0) `div` 2
+
+toDouble :: Integral a => a -> Double        
+toDouble n = (fromIntegral n) :: Double
+
+matching :: Eq a => [a] -> [a] -> Int -> Int
+matching s1 s2 d = length $ filter 
+                   (\(c,i) -> not (null (matches s2 c i d))) 
+                   (zip s1 [0..])
+
+matches :: Eq a => [a] -> a -> Int -> Int -> [Int]
+matches str c i d = filter (<= d) $ map (dist i) (elemIndices c str)
+  where dist a b = abs $ a - b
+

Ch03/Code10_jw/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0310 *~ 

Ch03/Code11_edit1/Code0311.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0311.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0311
+version:             0.1.0.0
+synopsis:            Fixing strings 1 edit distance away.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0311
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code11_edit1/Main.hs

@@ -0,0 +1,39 @@
+import Data.Char (toLower)
+import Data.List (group, sort)
+
+main = print $ edits1 "hi"
+
+-- Finds words one edit distance away  
+edits1 :: String -> [String]
+edits1 word = unique $ deletes ++ transposes ++ replaces ++ inserts
+  where splits     = [ (take i word', drop i word') | 
+                       i <- [0..length word']]
+        deletes    = [ a ++ (tail b) | 
+                       (a,b) <- splits, (not.null) b]
+        transposes = [ a ++ [b!!1] ++ [head b] ++ (drop 2 b) | 
+                       (a,b) <- splits, length b > 1 ]
+        replaces   = [ a ++ [c] ++ (drop 1 b) | 
+                       (a,b) <- splits, c <- alphabet, (not.null) b ]
+        inserts    = [a ++ [c] ++ b | 
+                      (a,b) <- splits, c <- alphabet ]
+        alphabet   = ['a'..'z']
+        word'      = map toLower word
+        
+unique :: [String] -> [String]
+unique = map head.group.sort
+
+{-
+edits1 :: [String] -> String
+edits1' ls = unique $ concat $ map edits1 ls
+
+editsN :: String -> Int -> [String]
+editsN word n = iterate edits1' (edits1 word) !! n
+-}
+
+edits1' :: [String] -> [String]
+edits1' ls = unique $ concat $ map edits1 ls
+
+editsN :: String -> Int -> [String]        
+editsN word n = iterate edits1' (edits1 word) !! n
+
+

Ch03/Code11_edit1/Makefile

@@ -0,0 +1,5 @@
+default:
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0311 *~ 

Ch03/Code12_spell/Code0312.cabal

@@ -0,0 +1,25 @@
+-- Initial Code0312.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                Code0312
+version:             0.1.0.0
+synopsis:            Spelling corrector.
+-- description:         
+homepage:            haskelldata.com
+license:             GPL-2
+license-file:        ../LICENSE
+author:              Nishant Shukla
+maintainer:          nick722@gmail.com
+-- copyright:           
+category:            Text
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+executable Code0312
+  main-is:             Main.hs
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.6 && <4.7, containers >=0.5 && <0.6
+  -- hs-source-dirs:      
+  default-language:    Haskell2010

Ch03/Code12_spell/Main.hs

@@ -0,0 +1,60 @@
+import Data.Char (isAlpha, isSpace, toLower)
+import Data.List (sort, group, maximumBy)
+import Data.Map (fromListWith, Map, member, (!))
+import Data.Ord (comparing)
+
+-- Corrects word spellings in a sentence
+autofix :: Map String Int -> String -> String
+autofix m sentence = unwords $ map (correct m) (words sentence)
+  
+getWords :: String -> [String]
+getWords str = words $ filter (\x -> isAlpha x || isSpace x) lower
+  where lower = map toLower str
+        
+train :: [String] -> Map String Int
+train = fromListWith (+) . (`zip` repeat 1)
+
+edits1 :: String -> [String]
+edits1 word = unique $ deletes ++ transposes ++ replaces ++ inserts
+  where splits     = [ (take i word', drop i word') 
+                     | i <- [0..length word'] ]
+        deletes    = [ a ++ (tail b) 
+                     | (a,b) <- splits, (not.null) b ]
+        transposes = [ a ++ [b !! 1] ++ [head b] ++ (drop 2 b) 
+                     | (a,b) <- splits, length b > 1 ]
+        replaces   = [ a ++ [c] ++ (drop 1 b) 
+                     | (a,b) <- splits
+                     , c <- alphabet
+                     , (not.null) b ]
+        inserts    = [ a ++ [c] ++ b 
+                     | (a,b) <- splits
+                     , c <- alphabet ]
+        alphabet   = ['a'..'z']
+        word'      = map toLower word
+
+knownEdits2 :: String -> Map String a -> [String]        
+knownEdits2 word m = unique $ [ e2 
+                              | e1 <- edits1 word
+                              , e2 <- edits1 e1
+                              , e2 `member` m]
+
+unique :: [String] -> [String]
+unique = map head.group.sort
+
+known :: [String] -> Map String a -> [String]
+known ws m = filter (`member` m) ws
+
+correct :: Map String Int -> String -> String                   
+correct m word = maximumBy (comparing (m!)) candidates
+  where candidates = head $ filter (not.null) 
+                     [ known [word] m 
+                     , known (edits1 word) m
+                     , knownEdits2 word m
+                     , [word] ]
+
+main :: IO ()
+main = do
+  rawText <- readFile "big.txt"
+  let m = train $ getWords rawText
+  let sentence = "such codez many hsakell very spel so korrect"
+  print $ autofix m sentence

Ch03/Code12_spell/Makefile

@@ -0,0 +1,6 @@
+default:
+	wget -N norvig.com/big.txt
+	cabal install --bindir=./
+
+clean:
+	rm -rf dist Setup.hs Code0312 big.txt *~ 

Ch03/LICENSE

@@ -0,0 +1,339 @@
+             GNU GENERAL PUBLIC LICENSE
+                Version 2, June 1991
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Ch03/README.md

@@ -6,8 +6,21 @@ Refer to the book for step-by-step explanations.
 
 <p align="center"><a href="http://haskelldata.com" target="_blank"><img src="http://haskelldata.com/images/ch03.png"/></a></p>
 
-# How to use
+# Recipes
+* **Code01**: Displaying a number in another base
+* **Code02**: Reading a number from another base
+* **Code03**: Searching for a substring using Data.ByteString
+* **Code04**: Searching a string using the Boyer–Moore–Horspool algorithm
+* **Code05**: Searching a string using the Rabin-Karp algorithm
+* **Code06**: Splitting a string on lines, words, or arbitrary tokens
+* **Code07**: Finding the longest common subsequence
+* **Code08**: Computing a phonetic code
+* **Code09**: Calculating the edit distance between two strings
+* **Code10**: Computing the Jaro–Winkler distance between two strings
+* **Code11**: Finding strings within one-edit distance
+* **Code12**: Fixing spelling mistakes using edit distance
 
+# How to use
 ### Setting up the environment
 Install the [Haskell Platform](http://www.haskell.org/platform/).