lista.rs

#![allow(dead_code)]
use crate::Lista::*;
use std::fmt;

enum Lista {
    Nodo(u32, Box<Lista>),
    Nil,
}

impl Lista {
    fn new() -> Lista {
        Nil
    }

    fn append(self, dato: u32) -> Lista {
        Nodo(dato, Box::new(self))
    }

    fn len(&self) -> u32 {
        match *self {
            Nodo(_, ref tail) => 1 + tail.len(),
            Nil => 0,
        }
    }
    
    fn stringify(&self) -> String {
        match *self {
            Nodo(head, ref tail) => {
                // `format!` is similar to `print!`, but returns a heap
                // allocated string instead of printing to the console
                format!("{}, {}", head, tail.stringify())
            },
            Nil => {
                format!("Nil")
            },
        }
    }
}

impl fmt::Display for Lista {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result  {
     write!(f ,"{}",self.stringify())
  }
} 

fn main() {
    let mut listita = Lista::new();
    println!("{}", listita.len());
    listita = listita.append(3);
    listita = listita.append(4);
    println!("{}", listita.len());
}