用Haskell编写的Python代码解析器

Haskell是一种纯粹的、函数式编程语言，而Python是一种面向对象的编程语言。在Haskell中编写Python代码解析器，可以通过解析Python代码，识别语法结构，并以Haskell的数据结构形式表示。下面是一个简单的Haskell程序，用于解析Python代码，并基于解析结果执行一些操作。

import Text.ParserCombinators.Parsec

-- 定义Python的语法结构
data PythonAST = Variable String
               | IntLiteral Int
               | StringLiteral String
               | FunctionCall String [PythonAST]
               | Assignment PythonAST PythonAST
               | If PythonAST [PythonAST] [PythonAST]
               deriving (Show)

-- 解析Python整数字面量
parseInteger :: Parser PythonAST
parseInteger = do
    value <- many1 digit
    return (IntLiteral (read value))

-- 解析Python字符串字面量
parseString :: Parser PythonAST
parseString = do
    char '"'
    value <- many (noneOf "\"")
    char '"'
    return (StringLiteral value)

-- 解析Python变量名
parseVariable :: Parser PythonAST
parseVariable = do
    first <- letter
    rest <- many (alphaNum <|> char '_')
    return (Variable (first:rest))

-- 解析Python函数调用
parseFunctionCall :: Parser PythonAST
parseFunctionCall = do
    name <- parseVariable
    args <- between (char '(') (char ')') (sepBy parseExpression (char ','))
    return (FunctionCall (getVarName name) args)

-- 解析Python赋值语句
parseAssignment :: Parser PythonAST
parseAssignment = do
    name <- parseVariable
    spaces
    char '='
    spaces
    value <- parseExpression
    return (Assignment (getVarName name) value)

-- 解析Python if语句
parseIf :: Parser PythonAST
parseIf = do
    string "if"
    spaces
    condition <- parseExpression
    spaces
    string ":"
    spaces
    trueBranch <- many parseExpression
    spaces
    string "else:"
    spaces
    falseBranch <- many parseExpression
    return (If condition trueBranch falseBranch)

-- 解析Python表达式
parseExpression :: Parser PythonAST
parseExpression = parseVariable
              <|> parseInteger
              <|> parseString
              <|> parseFunctionCall
              <|> parseAssignment
              <|> parseIf

-- 辅助函数，从语法结构中提取变量名
getVarName :: PythonAST -> String
getVarName (Variable name) = name
getVarName _ = error "Expected a Variable"

-- 解析Python代码
parsePythonCode :: Parser [PythonAST]
parsePythonCode = do
    result <- sepBy parseExpression (char '
')
    return result

-- 解析并执行Python代码
runPythonCode :: String -> [PythonAST]
runPythonCode input = case parse parsePythonCode "" input of
    Left err -> error $ "Parse Error: " ++ show err
    Right ast -> ast

-- 使用示例
main :: IO ()
main = do
    let code = "x = 5
"
               ++ "print(x)
"
               ++ "if x > 10:
"
               ++ "    print(\"x is greater than 10\")
"
               ++ "else:
"
               ++ "    print(\"x is less than or equal to 10\")"
    let ast = runPythonCode code
    putStrLn ("Python AST: " ++ show ast)

在上面的代码中，我们使用了Haskell的Parsec库来实现Python代码的解析。我们定义了Python的语法结构，并使用Parser Combinators解析器将Python代码转换为这些语法结构。使用示例中的Python代码，我们可以看到解析结果的Haskell表示形式。你可以根据需要修改和扩展这个简单的解析器，以支持更多的Python语法结构和功能。