用Haskell的Parsec解析浮点数

type Parser a = Parsec String () a

import Text.Parsec
import Text.Parsec.String (Parser)

-- 定义一个解析浮点数的解析器
floatParser :: Parser Double
floatParser = do
    integerPart <- many1 digit
    optional (char '.' >> many1 digit)
    return (read (integerPart ++ "." ++ replicate (length digits) '0'))
  where
    digits = filter (`elem` ".") integerPart

-- 测试解析器
main :: IO ()
main = do
    let testCases = ["123.45", "678", "9.0", "abc"]
    mapM_ (runParser floatParser () "") testCases

import Text.Parsec.Error (ParseError)

runParser :: Parser a -> SourceName -> String -> Either ParseError a
runParser parser source input = parse parser source input

parseTest :: Parser a -> String -> IO ()
parseTest parser input = case runParser parser "" input of
    Left err -> putStrLn $ "Parse error at " ++ show err
    Right result -> putStrLn $ "Parsed: " ++ show result