#[derive(Debug, PartialEq)]

#[derive(Debug, PartialEq)]

}
#[cfg(test)]
mod tests {
    use crate::parser::{parse, Expr};
    #[test]
    fn parse_ascii() {
        assert_eq!(parse(b"a"), Ok(Expr::Char(b'b')))
    }
    #[test]
    fn parse_dot() {
        assert_eq!(parse(b"."), Ok(Expr::Dot))
    }
    #[test]
    fn parse_concatenation() {
        assert_eq!(parse(b"ab"), Ok(Expr::Conc(Box::new(Expr::Char(b'a')), Box::new(Expr::Char(b'b')))));
    }
    #[test]
    fn parse_alternation() {
        assert_eq!(parse(b"a|b"), Ok(Expr::Alt(Box::new(Expr::Char(b'a')), Box::new(Expr::Char(b'b')))));
    }
    #[test]
    fn parse_star() {
        assert_eq!(parse(b"a*"), Ok(Expr::Star(Box::new(Expr::Char(b'a')))))
    }
    #[test]
    fn parse_plus() {
        assert_eq!(
            parse(b"a+"),
            Ok(Expr::Conc(
                Box::new(Expr::Char(b'a')),
                Box::new(Expr::Star(
                    Box::new(Expr::Char(b'a')))))))
    }
    #[test]
    fn parse_question() {
        assert_eq!(parse(b"a?"), Ok(Expr::Quest(Box::new(Expr::Char(b'a')))))
    }
    #[test]
    fn parse_star_before_concatenation() {
        assert_eq!(
            parse(b"ab*"),
            Ok(Expr::Conc(
                Box::new(Expr::Char(b'a')),
                Box::new(Expr::Star(
                    Box::new(Expr::Char(b'b')))
                ))
            )
        )
    }
    #[test]
    fn parse_quest_before_concatenation() {
        assert_eq!(
            parse(b"ab*"),
            Ok(Expr::Conc(
                Box::new(Expr::Char(b'a')),
                Box::new(Expr::Quest(
                    Box::new(Expr::Char(b'b')))
                ))
            )
        )
    }

    #[test]
    fn parse_plus_before_concatenation() {
        assert_eq!(
            parse(b"ab+"),
            Ok(Expr::Conc(
                Box::new(Expr::Char(b'a')),
                Box::new(Expr::Quest(
                    Box::new(Expr::Char(b'b')))
                ))
            )
        )
    }
    #[test]
    fn no_star_after_alternation() {
        assert!(matches!(
            parse(b"|*"),
            Err(_)
        ))
    }
    #[test]
    fn no_plus_after_alternation() {
        assert!(matches!(
            parse(b"|+"),
            Err(_)
        ))
    }
    #[test]
    fn no_quest_after_alternation() {
        assert!(matches!(
            parse(b"|?"),
            Err(_)
        ))
    }