Summary of Rust Constants

In Rust, constants serve as a means to define values that remain unchanged throughout the program's execution. Defined using the const keyword, constants have several important characteristics that distinguish them from variables.

Key Concepts

• Immutability: Constants are inherently immutable, meaning their value cannot be altered once set.
• Type Annotation: Unlike variables, constants must include a type annotation during their declaration.
• Scope: The scope of constants is similar to that of variables; they can be accessed anywhere within the module in which they are defined.
• Global: Constants can be declared in the global scope, making them accessible throughout the entire program.

Defining Constants

Constants in Rust are defined using the const keyword, followed by the name, type, and value. The syntax is as follows:

const NAME: TYPE = VALUE;

Example

Below is a simple example demonstrating how to define and use constants in Rust:

const PI: f64 = 3.14159;
const MAX_POINTS: u32 = 100_000;

fn main() {
    println!("Value of PI: {}", PI);
    println!("Maximum points: {}", MAX_POINTS);
}

Differences Between Constants and Variables

• Declaration: Constants are declared using const, whereas mutable variables are declared with let and can be modified.
• Memory: Constants are inlined at compile time, potentially leading to performance benefits.

Summary

In conclusion, constants in Rust provide a robust way to define values that remain unchanged throughout a program's execution. Clearly defined with type annotations, constants promote better code organization and clarity, and can be utilized in any scope where they are declared.