annoyingecho.rs

use std::io;
use std::io::Write;

fn main() {
    //println! is a macro that writes a line to stdout and then flushes the
    //stdout buffer
    println!("The inredibly annoying Rust echo strikes again!");

    //get a reference to stdin 
    let stdin = io::stdin();

    //create a mutable string to hold what the user types. 
    let mut buffer = String::new();
    
    //loop is a keyword for intentionally declaring an infinite loop.
    // `while true` would give a compiler warning. 
    loop { 
        //print! is like println!, but it doesn't append a newline, and it doesn't
        //flush stdout
        print!(">>>");

        //manually flush stdout so that ">>>" prompt appears 
        io::stdout().flush().expect("Could not flush stdout. Panic!");
   
        //stdout.flush() and stdin.readline() both return a Result, which is 
        //an enumerated type, that is either Ok, or some error. 
        //the expect() call tells the compiler, basically, "on Ok do nothing,
        //but on Error, fail with this message"
        stdin.read_line(&mut buffer).expect("Could not read stdin. Panic!");

        //echo back the user's input, because we're incredibly annoying
        println!("Haha! {}", buffer.trim());

        //clear the input string; only echo the most recent input. 
        buffer.clear();
    }   
}