Guessing Game Tutorial from Rust docs using the `print!` macro.

rust_guessing_game_print.rs

extern crate rand;          // rand crate for generating random numbers

use std::io;                // io library from standard library
use std::io::Write;         // Needed for flushing stdout after print.
use std::cmp::Ordering;     // For comparing values
use rand::Rng;              // from rand crate

fn main() {
    println!("Guess the number, from 0 to 100.");           // Greet user
    let secret_number = rand::thread_rng().gen_range(0, 101);

    loop {
        print!("Please input your guess: ");                // Prompt user
        io::stdout().flush().unwrap();                      // Flush
        let mut guess = String::new();                      // Allocate new mutable String

        io::stdin().read_line(&mut guess)
            .expect("Failed to read line");                 //

        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_)  => continue,
        };

        println!("You guessed: {}", guess);

        match guess.cmp(&secret_number) {
            Ordering::Less      => println!("Your guess was too small."),
            Ordering::Greater   => println!("Your guess was too big."),
            Ordering::Equal     => {
                println!("You win!");
                break;
            }
        }
    }

    println!("The secret number is: {}", secret_number);
}