What is the difference between let and const in Rust?

Question

Aryan Kumar · Answer

The let and const keywords in Rust are used to declare variables. However, there are some key differences between the two keywords.

Scope: let variables are scoped to the block in which they are declared, while const variables are scoped to the entire module in which they are declared.
Mutability: let variables are mutable by default, while const variables are immutable.
Initialization: let variables can be initialized with any expression, while const variables must be initialized with a constant expression.

Here is a table that summarizes the differences between let and const:

Feature	let	const
Scope	Block	Module
Mutability	Mutable	Immutable
Initialization	Any expression	Constant expression

Here is an example of how to use let and const:

Rust

fn main() {
  // `let` variable.
  let x = 5;

  // `const` variable.
  const Y: i32 = 10;

  // The `x` variable can be mutated.
  x = 10;

  // The `Y` variable cannot be mutated.
  // Y = 20; // This will compile an error.
}

In this example, the x variable is declared using the let keyword and initialized with the value 5. The Y variable is declared using the const keyword and initialized with the value 10. The x variable can be mutated, while the Y variable cannot be mutated.

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What is the difference between let and const in Rust?

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