Variables

Certainly! Here’s a description of let, mutability, shadowing, and const in Rust, each explained in separate points:

let:

• The let keyword is used to create variables in Rust.
• Variables created with let are immutable by default, meaning their values cannot be changed once assigned.
• The type of the variable can be inferred by the compiler based on the assigned value, or it can be explicitly specified using type annotations.
• Syntax: let variable_name = value;

Mutability:

• Rust promotes a default pattern of immutability for variables to ensure safer and more predictable code.
• To create mutable variables, you need to explicitly declare them as mutable using the let mut syntax.
• Mutable variables allow changing their values after assignment.
• Syntax: let mut variable_name = value;

Shadowing:

• Shadowing is the process of creating a new variable with the same name as an existing variable, effectively “shadowing” the original variable.
• Shadowing allows you to reuse variable names while changing their type or value.
• It is different from mutability because it creates a new variable rather than modifying the existing one.
• Shadowed variables can have different types, allowing flexibility in the program.
• Syntax: let variable_name = new_value;

const:

• Constants are values that are not allowed to change throughout the execution of a program.
• Constants are always immutable, and their values must be known at compile-time.
• They are declared using the const keyword and require explicit type annotations.
• Constants are typically written in uppercase with underscores separating words.
• Constants can be set only to a constant expression and not to the result of a function call or any other value that will be computed at runtime.
• Constants can be declared in any scope, including the global scope, which makes them useful for values that many parts of the code need to know about.
• Constant declaration must have a specified data type.
• Syntax: const CONSTANT_NAME: Type = value;

It’s important to note that let and const are used for creating variables, while mutability and shadowing determine how the variables can be modified or reassigned.

Examples:-

let x = 100;
x = 150; // error x is immutable by default and cannot be changed
let x = 200; // allowed since the varible x is re-initallised. This is called shadowing
let mut y = 150; // declared immutable can can be changed
y = 20; // allowed
const SCORE_LIMIT: u32 = 100;