#[derive(Clone, Debug, PartialEq)] pub enum Token { Symbol(char), Integer(i32), OpenParen, CloseParen, Plus, Minus, Times, Divide, Caret, } impl Token { pub fn starts_expression(&self) -> bool { match self { Token::OpenParen => true, Token::Symbol(_) => true, Token::Integer(_) => true, _ => false, } } }