Debug Print

fn main(){
    let my_number = {
        second_number = 8;
        second_number + 7;
    }
    println!("{}" , second_number); // 🛑 This is an error. because my_number will return ()
}

with this code block we will have two issues.

#![allow(unused)]
fn main() {
println!("{}" , second_number);
//                ^^^^^^^^^^^^ `()` cannot be formatted with the default formatter
//the trait `std::fmt::Display` is not implemented for `()`
}

the trait std::fmt::Display is not implemented for ()

that means () does not have the power of 'Display'

🚀 Trait = power for types

We have to use debug printing {:?}

or pretty debug printing {:#?}

fn main(){
    let my_number = {
        let second_number = 8;
        second_number + 7;
    };
    println!("output is: {:?}" , my_number); // => output is: ()
}