有偿实现 rust 实现简单的语法树

需要实现两个类中的方法 expression.rs 类

#[derive(PartialEq)] pub enum Expression{}

impl Display for Expression{ fn fmt(&self, f : &mut std::fmt::Formatter<'_>) -> Result<(), Error>{ unimplemented!() } }

impl Expression {

pub fn eval(&self) -> Result<Expression, String>{
    unimplemented!()
}

}

parse.rs 类 pub struct Parser {}

impl Parser { pub fn new(program : &str) -> Self { unimplemented!() }

pub fn parse(&mut self) -> Result<Expression, String>{
    unimplemented!()
}

}

测试用例： #[test] fn parse_var(){ let mut prog = Parser::new(&"x"); let result = prog.parse(); assert!(result.is_ok()); let e = result.unwrap(); assert_eq!("x", format!("{}", e)); }

#[test]
fn parse_int(){
    let mut prog = Parser::new(&"123");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("123", format!("{}", e));
}

#[test]
fn parse_bool(){
    let mut prog = Parser::new(&"T");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("T", format!("{}", e));
}

#[test]
fn parse_plus(){
    let mut prog = Parser::new(&"+(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 + 1", format!("{}", e));
}

#[test]
fn parse_minus(){
    let mut prog = Parser::new(&"-(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 - 1", format!("{}", e));
}

#[test]
fn parse_mult(){
    let mut prog = Parser::new(&"*(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 * 1", format!("{}", e));
}

#[test]
fn parse_div(){
    let mut prog = Parser::new(&"/(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 / 1", format!("{}", e));
}

#[test]
fn parse_lt(){
    let mut prog = Parser::new(&"<(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 < 1", format!("{}", e));
}

#[test]
fn parse_not(){
    let mut prog = Parser::new(&"!T");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("!T", format!("{}", e));
}

#[test]
fn parse_eq(){
    let mut prog = Parser::new(&"=(1, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("1 = 1", format!("{}", e));
}

#[test]
fn parse_func(){
    let mut prog = Parser::new(&"func x => T");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("func x => T", format!("{}", e));
}

#[test]
fn parse_app(){
    let mut prog = Parser::new(&"apply(func x => x, 1)");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("func x => x (1)", format!("{}", e));
}

#[test]
fn parse_if(){
    let mut prog = Parser::new(&"if <(1, 5) then 8 else 9");
    let result = prog.parse();
    assert!(result.is_ok());
    let e = result.unwrap();
    assert_eq!("if 1 < 5 then 8 else 9", format!("{}", e));
}

要求，通过测试用例即可，最好今天能完成。有意联系 @abcdef_d