concat.rs

pub fn main() {
    let mut str1 = format!("fellow ");
    //let str2 = format!("Rustaceans");
    let str2 = str1.clone();
    strcat(&mut str1, &str2);
    println!("{}", str1);
    println!("{}", concat(&str1, &str1));
}

/// Concatenate `suffix` onto the end of `prefix`.
fn strcat(prefix: &mut String, suffix: &String){
    for ch in suffix.chars() {
        prefix.push(ch);
    }
}

fn concat(car: &String, cdr: &String) -> String{
    let mut result = format!("");
    for ch in car.chars(){
        result.push(ch);
    }
    for ch in cdr.chars(){
        result.push(ch);
    }
    result
}
    

// Challenge: Convert `strcat` to use borrowing, not ownership.

// Question: Now that you've converted `strcat`, what happens if you
// call `strcat` using the same string for `prefix` and `suffix`?
// Why?