设计一个简单的语法分析器，能够将输入的单词序列分析成语法树，支持语法规则、优先级等特性。代码

好的，我可以给你一个简单的语法分析器的代码示例，它可以将输入的表达式转换成语法树。这个示例使用了递归下降解析算法。

class Node:
    def __init__(self, value, children=None):
        self.value = value
        self.children = children or []

    def __str__(self):
        if not self.children:
            return str(self.value)
        return f"({self.value} {', '.join(str(c) for c in self.children)})"

class Lexer:
    def __init__(self, source):
        self.source = source.strip()
        self.pos = 0

    def next_token(self):
        if self.pos >= len(self.source):
            return None

        if self.source[self.pos].isdigit():
            start = self.pos
            while self.pos < len(self.source) and self.source[self.pos].isdigit():
                self.pos += 1
            return int(self.source[start:self.pos])

        if self.source[self.pos] in "+-*/()":
            token = self.source[self.pos]
            self.pos += 1
            return token

        raise ValueError(f"Invalid character: {self.source[self.pos]}")

class Parser:
    def __init__(self, source):
        self.lexer = Lexer(source)
        self.current_token = self.lexer.next_token()

    def parse(self):
        return self.parse_expression()

    def parse_expression(self):
        node = self.parse_term()

        while self.current_token in "+-":
            operator = self.current_token
            self.consume_token()
            right = self.parse_term()
            node = Node(operator, [node, right])

        return node

    def parse_term(self):
        node = self.parse_factor()

        while self.current_token in "*/":
            operator = self.current_token
            self.consume_token()
            right = self.parse_factor()
            node = Node(operator, [node, right])

        return node

    def parse_factor(self):
        if self.current_token == "(":
            self.consume_token()
            node = self.parse_expression()
            if self.current_token != ")":
                raise ValueError("Expected ')'")
            self.consume_token()
            return node

        if isinstance(self.current_token, int):
            node = Node(self.current_token)
            self.consume_token()
            return node

        raise ValueError(f"Expected a number or '('")

    def consume_token(self):
        self.current_token = self.lexer.next_token()

if __name__ == '__main__':
    parser = Parser("2 + 3 * (4 - 1)")
    ast = parser.parse()
    print(ast)

这个示例将输入的表达式转换成语法树，并输出语法树的字符串表示。例如，输入 "2 + 3 * (4 - 1)"，输出 "(+ 2 (* 3 (- 4 1)))"。