Variables & Mutability

Importante Terms

Mutability

In rust, variables are inmutables by default. To make a variable mutable, you have to write before the variable the word mut, Here is an example:

use std::io;

fn main () {
	let mut name = "Value 1";
	
	print("old value of 'name': {name}")
	
	io::stdin().read_line(&mut name)
		.expect("Something has gone wrong");
		
	print("new value of 'name': {name}")
}

First, we define a varaible with a value of Value 1, later name value is printed. After that we use stdin to enter a new value for name then we use &mut name to shadow the value of name and rename that. At the end we printed it.

Constants

const TWO_HOURS_INS_SEC = 2 * 60 * 60;

Shadowing

It means that you can overwrite a value in a variable, without the necessity to create another instance. Example:

fn main () {
	let x = 10;
	println!("First Value of x: {x}");
	let x = x + 5;
	println!("Overwritting x value: {x}");
}

First value of x: 10
Overwritting x value: 15

Within inner Scope

To create an inner scope, you have to use {} indicating a inner scope was created. Inside this, the value of x will change until scope ends, then x return to the original value

fn main () {
	let x = 10;
	println!("First Value of x: {x}");
	
	{
		let x = x - 5;
		println!("x Value within inner scope {x}");
	}
	let x = x + 5;
	println!("Overwritting x value: {x}");
}