class Parser:
    lexer = None

    def __init__(self, lexer):
        return

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

    def move(self):
        return

    def error(self, msg):
        return

    def match(tag):
        return

    # bool = bool "||" join | join.
    def bool(self):
        return

    # join = join "&&" equality | equality.
    def join(self):
        return

    # equality = equality "==" relation | equality "!=" relation | relation.
    def equality(self):
        return

    # relation = expression "<" expression | expression "<=" expression | expression ">=" expression | expression ">" expression | expression.
    def relation(self):
        return

    # expression = expression "+" term | expression "-" term | term.
    def expression(self):
        return

    # term = term "*" unary | term "/" unary | unary.
    def term(self):
        return

    # unary = "!" unary | "-" unary | factor.
    def unary(self):
        return

    # factor = "(" bool ")" | ident | integer | "true" | "false".
    def factor(self):
        return

    # ident_list = ident { "," ident }.
    def ident_list(self):
        return

    # expression_list = expression { "," expression }.
    def expression_list(self):
        return

    # program = function { function }.
    def program(self):
        return

    # function = "fun" ident "[" [ ident_list ] "]" statements "end".
    def function(self):
        return

    # statements = statement { nl statement }.
    def statements(self):
        return

    # statement = [ if_statement | while_statement | assignment | function_call | return_statement ].
    def statement(self):
        return

    # if_statement = "if" expression statements [ "else" statements ] "end".
    def if_statement(self):
        return

    # while_statement = "while" expression statements "end".
    def while_statement(self):
        return

    # assignment = ident "=" expression.
    def assignment(self):
        return

    # function_call = ident "[" [ expression_list ] "]".
    def function_call(self):
        return

    # return_statement = "@" expression.
    def return_statement(self):
        return