Learn some Rust

Learn some rust

To install visit here.

Create a rust project by running

> cargo new learn_rust

The project structure

hello-rust
|- Cargo.toml
|- src
  |- main.rs

Cargo.toml == package.json

cargo add ferris-says@0.2 == npm install ferris-says@0.2

cargo build == npm i

cargo run == npm run start

Let's skip the hello world since no one cares.

Following the rust lang book, we can build a guessing game.

use colored::*;
use rand::Rng;
use std::{cmp::Ordering, io};

fn main() {
    let mut s = String::new();
    let secret = rand::thread_rng().gen_range(1..100);

    loop {
        println!("Type your input");
        io::stdin().read_line(&mut s).expect("something's wrong");

        let guess: u32 = match s.trim().parse() {
            Ok(num) => num,
            Err(e) => {
                println!("{}", e);
                println!("Please type a number");
                continue;
            }
        };

        println!("your input is: {}", s);
        match guess.cmp(&secret) {
            Ordering::Less => println!("{}", "Too small, try something bigger.".red()),
            Ordering::Greater => println!("{}", "Too big, try something smaller.".red()),
            Ordering::Equal => {
                println!("{}", "You win!".green());
                break;
            }
        }
    }
}

There's something interesting here, io::stdin().read_line(&mut s) returns a type called Result<..>. I understand this as a sync version of promise in JS. We can either just return the result (in this case the user input) with expect that acts like a catch or we can use match to create "call back"s for Ok - a successful case and Err - a panic case.

One other thing is my code doesn't work well after the first input - whatever input comes after the first one will become invalid.

By taking a closer look, mine seems to put the buffer string outside of the loop and all the input will be appended to the string with a new line character. So adding s.clear() in the first line of the loop fixed my code.