Where we bind a variable

We need to prepare

• A project called variables
• A println! call with an argument

Variables are a way to reuse certain values in your program. We start from the a familiar println! expression.

println!("Hello, {}!", "world");

If we would also want to say Goodbye, world!, this could be achieved by adding the following line.

println!("Goodbye, {}!", "world");

But what if we would want to say hello and goodbye to the moon? We would have to change the argument to the two println!.

println!("Hello, {}!", "moon");
println!("Goodbye, {}!", "moon");

Which seem wasteful. Let's see how a variable can help in this situation.

With let we can introduces a variable subject with the value world, that is used as an argument in the println! call.

let subject = "world";

println!("Hello, {}!", subject);
println!("Goodbye, {}!", subject);

Saying goodbye to moon can be achieved by changing the subject to moon.

let subject = "moon";

And there you have it, we bound a variable.