Difference between revisions of "Rust-Programming-Language/C2/Variables-and-Mutability/English"

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{| border="1"
 
{| border="1"
 
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|| '''Narration'''
 
|| '''Narration'''
 
|-
 
|-
−
|| '''Show Slide 1''':  
+
|| Show Slide:  
  
 
'''Title Slide'''
 
'''Title Slide'''
 
|| Welcome to the Spoken Tutorial on '''Variables '''and''' Mutability '''in '''Rust.'''
 
|| Welcome to the Spoken Tutorial on '''Variables '''and''' Mutability '''in '''Rust.'''
 
|-  
 
|-  
−
|| '''Show Slide 2''':
+
|| '''Slide 2'''
  
 
'''Learning Objective'''
 
'''Learning Objective'''
 
|| In this tutorial, we will learn about:
 
|| In this tutorial, we will learn about:
−
* Variables  
+
* Variables and
−
* Mutability and
+
* Mutability
−
* Data types
+
−
 
+
−
|-
+
−
||  '''Show Slide 3''':
+
  
 +
|-
 +
|| '''Slide 3'''
  
 
'''System Requirements'''
 
'''System Requirements'''
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* '''Rust 1.80.0 '''
 
* '''Rust 1.80.0 '''
 
* '''Visual Studio Code 1.19.0'''
 
* '''Visual Studio Code 1.19.0'''
−
|-
 
−
||  '''Show Slide 4''':
 
  
 +
|-
 +
|| '''Slide 4'''
  
 
'''Prerequisites'''
 
'''Prerequisites'''
−
 
−
'''https://spoken-tutorial.org'''
 
 
|| To follow this tutorial,
 
|| To follow this tutorial,
 
* You should be familiar with compiling and running a '''Rust''' program
 
* You should be familiar with compiling and running a '''Rust''' program
−
* If not, please go through the prerequisite '''Rust''' tutorial on this website.
 
  
−
|-
 
−
||  '''Show Slide 5''':
 
  
 +
|-
 +
|| '''Slide 5'''
  
 
'''Code Files'''
 
'''Code Files'''
−
||  
+
||
−
* The files used in this tutorial are provided in the '''Code files''' link of this tutorial page
+
* The following code file required to practise this tutorial
−
* Please download and extract the files.
+
* This file is provided in the Code Files link of this tutorial page
−
* Make a copy and then use them while practicing.
+
  
 
|-  
 
|-  
−
|| '''Show Slide 6''':
+
|| '''Slide 6'''
−
 
+
 
'''Variables'''
 
'''Variables'''
 
let a = 10; //immutable
 
let a = 10; //immutable
 
let mut b=15;//mutable
 
let mut b=15;//mutable
−
|
+
||
 
* In Rust, we create variables using the '''let''' statement.
 
* In Rust, we create variables using the '''let''' statement.
 
* By default, variables are immutable,meaning their values cannot be changed
 
* By default, variables are immutable,meaning their values cannot be changed
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We can see a terminal window at the bottom.
 
We can see a terminal window at the bottom.
 
|-  
 
|-  
−
|| Type at the prompt:  
+
|| Type at the prompt:  
  
 
'''cargo new variables'''
 
'''cargo new variables'''
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fn main(){
 
fn main(){
 +
 
let a = 1;
 
let a = 1;
 +
 
println!(“The value of a is {}”,a);
 
println!(“The value of a is {}”,a);
 +
 
a=2;
 
a=2;
 +
 
println!(“The value of a is {}”,a);
 
println!(“The value of a is {}”,a);
 +
 
}
 
}
 
|| '''let''' keyword is used to declare variables in '''Rus'''t.
 
|| '''let''' keyword is used to declare variables in '''Rus'''t.
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|-  
 
|-  
 
||  
 
||  
−
|| In the menu bar, click on terminal and select '''New Terminal.'''
+
|| In the menu bar, click on '''Terminal''' and select '''New Terminal.'''
  
 
|-  
 
|-  
 
|| Type Cargo build
 
|| Type Cargo build
−
|| In the terminal, type '''cargo build '''to compile the Cargo project.
+
|| In the terminal, type '''cargo build '''to compile the '''Cargo''' project.
  
 
|-  
 
|-  
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|| We can see the output.
 
|| We can see the output.
  
−
Both the '''initialized '''and the modified values are printed successfully.
+
Both the '''initialized '''and modified values are printed successfully.
 
|-  
 
|-  
 
||  
 
||  
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|-  
 
|-  
 
|| '''Shadowing'''
 
|| '''Shadowing'''
−
 
−
'''fn main() {'''
 
−
'''let x = 5;'''
 
−
'''println!("x is {}", x);'''
 
−
 
−
'''let x = x + 2;'''
 
−
'''println!("x is {}", x);'''
 
−
'''}'''
 
  
 
|| Clear the code window and then copy and paste the code from the code file.
 
|| Clear the code window and then copy and paste the code from the code file.
  
 
Rust allows variable shadowing.
 
Rust allows variable shadowing.
 +
 
Here the variable '''x''' is shadowing.
 
Here the variable '''x''' is shadowing.
 +
 
Shadowing is to declare a new variable with the same name as a previous variable in the same scope.
 
Shadowing is to declare a new variable with the same name as a previous variable in the same scope.
 +
 
We can assign a new value to the new variable while the old variable remains unchanged.
 
We can assign a new value to the new variable while the old variable remains unchanged.
 +
 
Save the file.
 
Save the file.
 
|-  
 
|-  
−
||  
+
|| type '''cargo run'''
 
|| In the terminal, type '''cargo run'''
 
|| In the terminal, type '''cargo run'''
  
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|| Clear the code window.
 
|| Clear the code window.
  
−
Copy and paste the code from the codefile.
+
Copy and paste the code from the code file.
  
 
In this code, observe the declaration of variables '''outer_var '''and''' inner_var.'''
 
In this code, observe the declaration of variables '''outer_var '''and''' inner_var.'''
  
−
Curly braces { } define the block scope where the variable access becomes restricted to local.  
+
Curly braces { } define the block scope where the variable access becomes restricted to the local.  
  
 
Save the program.
 
Save the program.
  
 
|-  
 
|-  
−
|| Ctrl + S
+
|| Type cargo run
 
|| Let us check the output. Run the program.
 
|| Let us check the output. Run the program.
  
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|-  
 
|-  
−
||  
+
|| Slide:
−
|| Next we will see about various data types in '''Rust'''.
+
−
|-
+
−
||  '''Show Slide 7''':
+
  
 +
'''Summary'''
 +
|| This brings us to the end of this tutorial.
  
−
'''Rust - Data types '''
+
Let us summarize.  
−
||
+
−
* Every value in '''Rust '''is of a certain '''Type.'''
+
−
* Rust is a statically typed language that checks the types of variables at compile time.
+
−
* Compiler must know the type of all variables at compile time
+
−
* This helps the '''compiler '''to optimize for efficient and faster '''runtime execution.'''
+
−
 
+
 
|-  
 
|-  
−
||'''Show Slide 8''':
+
|| Slide:
  
−
'''Scalar Type'''
+
Assignment
−
|| Data types are divided as
+
−
* Scalar and Compound Types
+
−
 
+
−
A Scalar Type is referred to as a single value. Rust has four Scalar Data types.
+
−
They are:
+
−
* Integers
+
−
* Float
+
−
* Boolean
+
−
* Character
+
−
 
+
−
|-
+
−
||
+
−
|| Switch back to the visual code editor.
+
−
|-
+
−
||
+
−
|| Let us see a rust program for various data types.
+
−
 
+
−
Copy paste the code from the code file.
+
−
|-
+
−
|| Highlight according to narration
+
  
 
fn main() {
 
fn main() {
−
let x: i32 = 100;
 
−
let y: u32 = 200;
 
−
let f: f64 = 3.14;
 
−
let flag: bool = true;
 
−
let character: char = 'R';
 
−
println!("Integer: {}", x);
 
−
println!("Integer: {}", y);
 
−
println!("Float: {}", f);
 
−
println!("Boolean: {}", flag);
 
−
println!("Character: {}", character);
 
  
−
}
+
let x = 10; // Immutable variable
−
||  We use integer data types to store whole numbers.
+
  
−
i''' '''specifies signed integer type i.e(it can store both positive or negative value)
+
println!("The value of x is: {}", x);
  
−
'''32 '''is the size of the data type i.e (it takes 32 bits of space in memory)
+
x = 20;
  
−
Integers can be of many types as i8, i16, i32, i64.
+
println!("The new value of x is: {}", x);
  
−
u specifies the unsigned integer type i.e (it can only store positive integer values.)
 
−
 
−
If we try to store negative numbers to u32 type variables, we will get an error.
 
−
 
−
Here, the '''f '''character represents a floating point number.
 
−
 
−
32 and 64 represent the size in bits.
 
−
 
−
A boolean data type can have two possible values: true or false.
 
−
 
−
'''char''' represents the character type variable and we use single quotes to represent a character.
 
−
 
−
We can also store special characters like $, & etc. using the character type.
 
−
 
−
Save the program.
 
−
|-
 
−
||
 
−
|  Let us compile and run the program and see the output.
 
−
|-
 
−
||
 
−
|| In the terminal, type '''cargo run.'''
 
−
 
−
We can see the various data types printed as output.
 
−
|-
 
−
|| '''Show Slide 9''':
 
−
 
−
'''Type Inference in Rust'''
 
−
||
 
−
* In Rust we can create variables without mentioning a data type
 
−
* let x=50;
 
−
* Rust will automatically set i32 as default type for integer by looking at the value 50.
 
−
* This process is Type Inference.
 
−
 
−
|-
 
−
|| '''Show Slide 10''':
 
−
 
−
'''Constants'''
 
−
const PI: f32 = 3.14159265358979323846;
 
−
fn main() {
 
−
let radius = 5.0;
 
−
let circumference = 2.0 * PI * radius;
 
−
println!("The circumference of a circle with radius {} is {}", radius, circumference);
 
−
}
 
−
|| This is an example for constants.
 
−
* Constants are variables that are immutable and have a fixed value.
 
−
* They are declared using the '''const''' keyword.
 
−
* You must declare the type of the value.
 
−
|-
 
−
||
 
−
|| This brings us to the end of this tutorial.
 
−
 
−
Let us summarize.
 
−
|-
 
−
|| '''Show Slide 11''':
 
−
 
−
'''Summary'''
 
−
|| In this tutorial, we learnt about
 
−
* Variables
 
−
* Mutability and
 
−
* Data types
 
−
 
−
|-
 
−
|| '''Show Slide 12''':
 
−
 
−
'''Assignment '''
 
−
 
−
fn main() {
 
−
let y: u32 = - 200;
 
−
println!("Integer: {}", y);
 
 
}
 
}
−
 
 
|| As an assignment, do the following.
 
|| As an assignment, do the following.
  
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|-
 
|-
−
|| '''Show Slide 13''':
+
|| Thank You
  
−
'''About Spoken Tutorial Project'''
+
We would like to thank '''Vishal Pokuri from VIT Vellore '''for content contribution.
−
|| The video at the following link summarizes the Spoken Tutorial project.
+
||  
−
 
+
−
Please download and watch it.
+
−
|-
+
−
|| '''Show Slide 14''':
+
−
 
+
−
'''Spoken Tutorial Workshops'''
+
−
|| The '''Spoken Tutorial Project '''Team conducts workshops and gives certificates.
+
−
 
+
−
For more details, please write to us.
+
−
|-
+
−
|| Slide : Forum for specific questions
+
−
|| Please post your timed queries in this forum
+
−
|-
+
−
|| '''Show Slide 15''':
+
−
|| Spoken Tutorial project was established by the Ministry of Education(MoE), Govt of India
+
−
|-
+
−
|| '''Show Slide 16''':
+
−
 
+
−
'''Thank You'''
+
−
 
+
−
|| We would like to thank '''Vishal Pokuri from VIT Vellore '''for content contribution.
+
−
|-
+
−
|| Thank You
+
−
|| This tutorial is contributed by '''Nirmala Venkat''' and '''Ketki Bhamble''' from the spoken tutorial team.
+
  
 
Thank you for joining.
 
Thank you for joining.
 
|-
 
|-
 
|}
 
|}

Latest revision as of 18:34, 4 August 2025

Visual Cue Narration
Show Slide:

Title Slide

Welcome to the Spoken Tutorial on Variables and Mutability in Rust.
Slide 2

Learning Objective

In this tutorial, we will learn about:
  • Variables and
  • Mutability
Slide 3

System Requirements

This tutorial is recorded using
  • Ubuntu Linux OS version 22.04
  • Rust 1.80.0
  • Visual Studio Code 1.19.0
Slide 4

Prerequisites

To follow this tutorial,
  • You should be familiar with compiling and running a Rust program


Slide 5

Code Files

  • The following code file required to practise this tutorial
  • This file is provided in the Code Files link of this tutorial page
Slide 6

Variables let a = 10; //immutable let mut b=15;//mutable

  • In Rust, we create variables using the let statement.
  • By default, variables are immutable,meaning their values cannot be changed
  • You can make them mutable by using mut.
Open Visual Studio Code editor Let us open the Visual Studio Code editor.
Open the terminal by pressing

Ctrl+Tilde (~)

Click on Terminal and select New Terminal.

In the menu bar, click on Terminal and select New Terminal.

We can see a terminal window at the bottom.

Type at the prompt:

cargo new variables

Go to our working directory MyRustProject as explained earlier.

Please refer to the Additional Reading material link of this tutorial. It explains the steps to create and run the project.

Type the command cargo new variables and press Enter

Open the created project as shown.

Point to main.rs file.

Press Ctrl + C to copy

Press Ctrl + V to paste

In the main.rs file, copy and paste the code from the codefile.
Highlight the code according to narration

fn main(){

let a = 1;

println!(“The value of a is {}”,a);

a=2;

println!(“The value of a is {}”,a);

}

let keyword is used to declare variables in Rust.

Here we have initialized the variable a and assigned the value 1 to it.

We are trying to reassign the value 2 to variable a.

After reassigning we are printing the variable’s value to see what the value contains.

Press Ctrl and S to save the file.

In the menu bar, click on Terminal and select New Terminal.
Type Cargo build In the terminal, type cargo build to compile the Cargo project.
Highlight the error Here, we can see an error - cannot assign twice to immutable variable ‘a’.

Note that we had mentioned variables are immutable by default.

So switch back to the program.
Type mut

Let mut a=1;

Now, type mut in between let and a.

Here we are telling the compiler that the initialized variable is mutable.

Type cargo run Save the file.

In the terminal, type cargo run

Highlight the output We can see the output.

Both the initialized and modified values are printed successfully.

Next let us see the shadowing of variables.
Shadowing Clear the code window and then copy and paste the code from the code file.

Rust allows variable shadowing.

Here the variable x is shadowing.

Shadowing is to declare a new variable with the same name as a previous variable in the same scope.

We can assign a new value to the new variable while the old variable remains unchanged.

Save the file.

type cargo run In the terminal, type cargo run

Check the output.

It prints the value of x as 5 and 7 as the result of shadowing.

Next we will see the scope of the variables.
Scope of the variable

fn main() {

// scope of outer_var variable is inside the main function code block

let outer_var = 100;

// start of the inner code block

{

// scope of inner_var variable is only inside this new code block

let inner_var = 200;

println!("inner_var = {}", inner_var);

}

// end of the inner code block

println!("inner_var = {}", inner_var);

println!("outer_var = {}", outer_var);

}

Clear the code window.

Copy and paste the code from the code file.

In this code, observe the declaration of variables outer_var and inner_var.

Curly braces { } define the block scope where the variable access becomes restricted to the local.

Save the program.

Type cargo run Let us check the output. Run the program.

We can see a compilation error.

Here we tried to print the inner_var outside of the inner code block.

So the program will give an error.

Let us comment the print statement of inner_var in the outer block.

Save the program.

Run the program again to see the output.

We can see the output displayed for outer_var as 100 and inner_var as 200.

This shows that any variable outside the braces will have global access.

Slide:

Summary

This brings us to the end of this tutorial.

Let us summarize.

Slide:

Assignment

fn main() {

let x = 10; // Immutable variable

println!("The value of x is: {}", x);

x = 20;

println!("The new value of x is: {}", x);

}

As an assignment, do the following.
  • Run the above program
  • Analyse the error and correct the program.
Thank You

We would like to thank Vishal Pokuri from VIT Vellore for content contribution.

Thank you for joining.

Contributors and Content Editors

Madhurig, Nirmala Venkat

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