50 lines
1.3 KiB
Haskell
50 lines
1.3 KiB
Haskell
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import Data.Typeable
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import Text.Parsec
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type Parser a = Parsec String () a
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whitespaces :: Parser String
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whitespaces = many (oneOf "\t ")
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number :: Parser String
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number = many1 digit
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number' :: Parser Int
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number' = do
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string_of_number <- many1 digit
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return (read string_of_number)
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isolatedNumber = do
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_ <- whitespaces
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n <- number
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_ <- whitespaces
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return n
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-- remove spaces at the begining and the end of a parser
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lexeme :: Parser a -> Parser a
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lexeme parser = do
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_ <- whitespaces
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res <- parser
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_ <- whitespaces
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return res
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main :: IO ()
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main = do
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test whitespaces "whitespaces" " "
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test whitespaces "whitespaces" "32"
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test number "number" "32"
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test number "number" " 32 "
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test number' "number'" "32"
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test number' "number'" " 32 "
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test isolatedNumber "isolatedNumber" " 32 "
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test isolatedNumber "isolatedNumber" " foo "
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test (lexeme number) "lexeme number" " 32 "
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test :: (Typeable a, Show a) => Parser a -> String -> String -> IO ()
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test parser description string = do
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putStrLn $ "-- " ++ description ++ " on '" ++ string ++ "'"
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let res = parse parser description string
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case res of
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Left err -> print err
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Right value -> putStr $ (show value) ++ " :: " ++ show (typeOf value)
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putStrLn "\n"
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