Difference between revisions of "Stupid Curry Tricks"
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Eric Gesell (talk | contribs) (Added code for frequency.hs) |
Tomjaguarpaw (talk | contribs) (Deleting page that hasn't been edited for over 10 years) |
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| − | This is a useless piece of code that counts and prints the number of times each character in the English alphabet occurs in a string. This version is hard-coded to read from the file "hi.txt", but it can easily be modified to interact with standard IO or read a file passed on the command line. The most interesting part is the use of currying to generate the counting functions. |
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| − | <haskell> |
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| − | --system to show character frequencies in a set of strings |
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| − | import System.IO |
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| − | import Data.Char(toLower) |
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| − | |||
| − | --letters to scan for |
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| − | letters = ['a'..'z'] |
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| − | |||
| − | --counts the ocurences of a particualr letter |
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| − | countLetters :: Char -> [Char] -> Int |
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| − | countLetters target str = length (filter (\c -> c == target) str) |
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| − | |||
| − | --creates a curryed version of countletters for a particular letter |
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| − | makeCounter :: Char -> ([Char] -> Int) |
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| − | makeCounter c = countLetters c |
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| − | |||
| − | --creates a countLetters funciton for each letter in the alphabet |
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| − | counters :: [([Char] -> Int)] |
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| − | counters = map makeCounter letters |
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| − | |||
| − | frequencies :: [([Char] -> Int)] -> [Char] -> [Int] |
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| − | frequencies [] _ = [] |
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| − | frequencies (f:fs) cs = (f cs) : frequencies fs cs |
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| − | freqs :: [Char] -> [(Char, Int)] |
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| − | freqs cs = zip letters (frequencies counters cs) |
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| − | |||
| − | --make pretty output |
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| − | prettyPrint :: (Char, Int) -> String |
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| − | prettyPrint (c, n) = [c] ++ ":" ++ (show n) ++ "\n" |
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| − | printList :: [(Char, Int)] -> String |
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| − | printList [] = [] |
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| − | printList ((c, i):frs) = ((c:[]) ++ ": " ++ (show i) ++ "\n") ++ printList frs |
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| − | --io and main program |
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| − | main = do |
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| − | str <- readFile "hi.txt" |
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| − | let out = (freqs (map toLower str)) |
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| − | putStrLn $ printList out |
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| − | </haskell> |
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