Log-space parentheses matcher.

parenmatch.py

def parens(s: str):
    def parser_paren(i: int) -> tuple[bool, int]:
        i += 1
        result = True
        while i < len(s) and result and s[i] != ")":
            if s[i] == "(":
                result, i = parser_paren(i)
            elif s[i] == "[":
                result, i = parser_bracket(i)
            else:
                return False, 0
        if not result:
            return False, 0
        if i > len(s) - 1:
            return False, 0
        return True, i+1

    def parser_bracket(i: int) -> tuple[bool, int]:
        i += 1
        result = True
        while i < len(s) and result and s[i] != "]":
            if s[i] == "(":
                result, i = parser_paren(i)
            elif s[i] == "[":
                result, i = parser_bracket(i)
            else:
                return False, 0
        if not result:
            return False, 0
        if i > len(s) - 1:
            return False, 0
        return True, i+1

    result, i = True, 0
    while i < len(s) and result:
        if s[i] == "(":
            result, i = parser_paren(i)
        else:
            result, i = parser_bracket(i)
    return result