Table of Contents📚
Variables📦
Declaring a variable
To declare a variable, we use the keyword let followed by the name of the variable, and the value of the variable.
let monkeys = 5;
We now have a variable monkeys with the value 5.
Printing a variable💬
We can now use the variable monkeys in our program.
For example, we can print the value of monkeys:
let x = 5;
println!("There are {} Monkeys 🐒", monkeys);
The {} is a placeholder for the value of x. It will be replaced by its value when the program is executed.
If we run the program, we will see the following output:
There are 5 Monkeys 🐒
This program does the same as if we had written:
println!("There are {} Monkeys 🐒", 5);
because monkeys is replaced by its value.
Modifying a variable
We can change the value of a variable by using the following syntax:
// declaring the variable
let dogs = 5;
// modifying the variable
dogs = 6;
But if we run this program, we will get the following error ⛔ :
We get this error because, by default, variables are immutable. It means that we can’t change their value.
Mutable variables
We can set the variable to be mutable by using the keyword mut before the name of the variable.
let mut dogs = 5;
dogs = 6;
println!("There are {} dogs 🐕", dogs);
Output:
There are 6 dogs 🐕