Variables

Variales are names given to computer memory location where your store data in a program. In Rust, we define variables with let:

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fn main() {
	let name = "osinfo";
	let number: u32 = 1;
	let array = [1,2,3,4];
}

In Rust we have two types of variables which are:

• Immutable variables: Default behaviour, you can’t modify its value.
• Mutable variables: You can modify the value of the variable.

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fn main () {
	let a: i32 = -5;     // Immutable variable
	let mut b: u32 = 9;  // Mutable variable
}

You have to specify mut to make variables mutable.

Constants

Constants are variables that can’t be converted to mutable by design and have an explicit data type.

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fn main () {
	const MAX_POINT: i32 = -5;    
}

Constants must be written in uppercase by convention.

Shadowing

Shadowing is a Rust concept of assigning a new value to an immutable variable. With an example is easier to understand:

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fn main () {
	let x: u32 = 4;
	let x: u32 = x +1
	
	println!("The value of x is: {}", x);
}

Rust programmers say that the first variable declaration is being shadowed by the second.

Shadowing vs Mutable variables

• Without using let, script will fail.
• You can only do certain transformations:
  • Change data type.
  • Change value adressing the previous value.
  • …
• After a modification has been made, the variable will remain immutable.