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import System.Environment
import Data.String.Utils
import qualified Data.List as List
main = do
args <- getArgs
let input = replace " " "" (head args)
print $ List.reverse $ List.sort $ countfreqs input 1 []
print $ List.reverse $ List.sort $ countfreqs input 2 []
print $ List.reverse $ List.sort $ countfreqs input 3 []
-- countfreqs s n []: calculate occurrence statistics of n-grams in s
countfreqs :: String -> Int -> [Freq] -> [Freq]
countfreqs "" _ fl = fl
countfreqs s n fl
| length s < n = fl
| otherwise = countfreqs (tail s) n (freqsincr fl (take n s) [])
-- freqsincr fl s []: add s to the frequencies in fl
freqsincr :: [Freq] -> String -> [Freq] -> [Freq]
freqsincr [] s fl = fl ++ [Freq { item = s, freq = 1}]
freqsincr (freq:fla) s2 flb
| get_item freq == s2 = fla ++ flb ++ [Freq { item = s2, freq = get_freq freq + 1}]
| otherwise = freqsincr fla s2 (flb ++ [Freq { item = get_item freq, freq = get_freq freq}])
-- Data type for keeping track of frequencies (Int) of substrings (String)
data Freq = Freq { item :: String, freq :: Int } deriving (Eq)
get_item :: Freq -> String
get_item = item
get_freq :: Freq -> Int
get_freq = freq
instance Ord Freq where
f1 `compare` f2 = get_freq f1 `compare` get_freq f2
instance Show Freq where
show f = get_item f ++ " (" ++ show (get_freq f) ++ "x)"
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