Bugl — code interview practice that feels like a game

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Flash cards

Review the key moves

1/4

Core idea

What is the main idea behind Rust Constants?

Lesson checks

Short Mimo-style checks built from this lesson's code, terms, and sequence.

1Quick choice

Which statement best captures the main point of this lesson?

2Fill blank

Complete the missing token from the example code.

___ BIRTHYEAR: i32 = 1980;

3Order

Put the learning moves in the order that makes the concept easiest to apply.

Constants vs Variables

Constants Must Have a Type

Creating a Constant

Constant variables are used to store values that never change.

Unlike regular variables, constants must be defined with a type (e.g. i32 or char ).

To create a constant, use the const keyword, followed by the name, type, and value:

const BIRTHYEAR: i32 = 1980;
const
MINUTES_PER_HOUR: i32 = 60;

You must write the type when creating a constant. You cannot let Rust guess the type like you can with regular variables:

const BIRTHYEAR: i32 = 1980; // Ok
const BIRTHYEAR = 1980; // Error: missing type

Another thing about constants, is that it is considered good practice to declare them with uppercase.

It is not required, but useful for code readability and common for Rust programmers:

Examples

Here's a quick comparison

Feature	Constant ( const )	Variable ( let )
Can change?	No	Yes, if mut is used
Type required?	Yes	No (optional)