Difference between revisions of "Anagrams"
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Revision as of 16:24, 9 June 2006
module Main (main) where
import System.Environment (getArgs)
import Data.Char (toUpper,isAlpha)
import Data.List (sortBy)
import Control.Monad (liftM)
import qualified Data.ByteString.Char8 as B
data CharCount = CharCount !Char !Int deriving (Show, Eq)
data WordData = WordData B.ByteString [CharCount] deriving (Show, Eq)
main :: IO ()
main =
do n < head `fmap` getArgs
wl < liftM makeWordList $ B.readFile n
user < liftM countChars B.getLine
case (findAnagrams wl user) of
[] > print "No anagrams."
x > B.putStr . B.unlines . map B.unwords $ x
findAnagrams :: [WordData] > [CharCount] > [[B.ByteString]]
findAnagrams [] _ = []
findAnagrams lst@((WordData bs cc):rest) qcc =
case (qcc `minus` cc) of
Nothing > remaining
Just [] > [bs]:remaining
Just x > map ((:) bs) (findAnagrams lst x) ++ remaining
where remaining = findAnagrams rest qcc
minus :: (Monad m) => [CharCount] > [CharCount] > m [CharCount]
minus x [] = return x
minus [] _ = fail "can't subtract from empty"
minus (lft@(CharCount c1 i1):xs) r@((CharCount c2 i2):ys)
 (c1 == c2) && (i2 == i1) = xs `minus` ys
 (c1 == c2) && (i2 < i1) = do rem < xs `minus` ys
return $! (CharCount c1 (i1  i2)):rem
 (c1 == c2) && (i2 > i1) = fail "right has more chars than left"
 (c1 > c2) = fail "right has chars not in left"
 (c1 < c2) = do rem < xs `minus` r
return $! lft:rem
 otherwise = error "Bad condition"
countChars :: B.ByteString > [CharCount]
countChars = map counts . B.group . B.sort . B.map toUpper . B.filter isAlpha
where counts x = CharCount (B.unsafeHead x) (B.length x)
makeWordList :: B.ByteString > [WordData]
makeWordList = map (\w > WordData w (countChars w)) . sortBy bsLenCmp . B.words
where bsLenCmp x y = compare (B.length y) (B.length x)