Month: January 2025

Functions in Rust

Functions are use to  efficient programming and eliminates the need to constantly rewrite code.

Rust is a strictly typed language and therefore needs to know the data type for all variables at compilation.

When there is not a specified return value, the function will return the unit data type which is represented as () and indicates there is no other meaningful values that could be returned. A statement does not return a value.

In the below example we can see how a function can be defined and called from the main.

Function without and with parameters. Define the parmeter data type and return data type.

fn main(){
    display_message();
    display_message_with_parameters(10);
    let addition  = add_numbers(10, 20);
    println!("Addition of 2 number is {}", addition);
}

fn display_message(){
    println!("Display message....");
}

fn display_message_with_parameters(value : i8){
    println!("Function paramter value is {}", value);
}

fn add_numbers(param1: i8, param2: i8) -> i8{
    param1 + param2
}

Output-

Display message....
Function paramter value is 10
Addition of 2 number is 30

Diverging Functions

Diverging functions never return. They are marked using !, which is an empty type.

fn foo() -> ! {
    panic!("This call never returns.");
}

Empty return functions

Function return empty (). It doesn’t return anything but returns back to caller

fn some_fn() {
    ()
}

fn main() {
    let _a: () = some_fn();
    println!("This function returns and you can see this line.");
}

Arrays and tuples in Rust

In Rust arrays are stored in contigious section of memory locations and sorted in order. They are fixed length and cannot be dynamically resize, containing elements of same data type.

A fix size array denotes [T;N]. where T denotes element type i.e. i32, u64 etc. and N denoted non-negative compile time constant size. This means compiler needs to know before running the code the size of array.

One way of declaring an array is to have the values comma seperated in square brackets e.g.- [1, 2, 3]

Example-

let fruits = ["apple", "orange"];
let selected_fruit = fruits[0];

// Retrieve first element of an array.
println!("Selected fruit is - {}", selected_fruit);

Output-

Selected fruit is - apple

To modify the value in the array make the array mutable and change the value of an element in array, in this case first element.

let mut fruits = ["apple", "orange"];
fruits[0]= "mango";

let selected_fruit = fruits[0];
println!("Selected fruit is - {}", selected_fruit);

Output-

Selected fruit is - mango

Repeat expression – Declaring arrays with the data type and length [expr, N] where N is the times to repeat expression (expr).

Note that [expr; 0] is allowed, and produces an empty array. This will still evaluate expr, however, and immediately drop the resulting value, so be mindful of side effects.

let numbers : [i32; 5]; // declare array
numbers= [1, 3, 5, 7, 9]; // initalize array
println!("Selected number - {}", numbers[0]); // print first element

Output-

Selected number - 1

Compiler Errors-

If array is not initalised and the element of array is tried to access the compiler thorws an error-

let numbers : [i32; 5];
println!("Selected number - {}", numbers[0]);

Solution-

let numbers : [i32; 5];
numbers = [0;5]; // All elements has value 0
println!("Selected number - {}", numbers[0]);

Output-

Selected number - 0

Compiler Errors-

Index out of bounds – if the element accessed is larger than the array length.

let numbers : [i32; 5];
println!("Selected number - {}", numbers[5]);

The array length is 5 and index starts from 0, so the last index is 4. But in above program the index 5 is trying to access hence error

Solution-

The element accessed here is the last element i.e. index 4.

let numbers : [i32; 5];
numbers = [0;5]; // all elements has value 0
println!("Selected number - {}", numbers[4]);/ Compiles successfully

Count of elements

Get the length of an array using extension function len()

let numbers : [i32; 5];
numbers = [0;5];
println!("Length of numbers is {}", numbers.len());

Output-

Length of numbers is 5

Slice Array

Sleic the arrary by giving an expression the starting and ending index with double dots between. e.g.- [starting_index..ending_index]. Access the memory of the variable and provide the range e.g.- &array_variable[2..4]

Print the array and the slice using {:?}

Omit start index and end index [..4] and [2..] respectively

let numbers : [i32; 5] = [10, 20, 30, 40, 50];
let array_slice = &numbers[2..4];
let omit_start_index = &numbers[..4];
let omit_end_index = &numbers[2..];
println!("array = {:?}", numbers);
println!("slice = {:?}", array_slice);
println!("omit start index = {:?}", omit_start_index );
println!("omit end index = {:?}", omit_end_index );

Output

array = [10, 20, 30, 40, 50]
slice = [30, 40] // [2..4]
omit start index = [10, 20, 30, 40] // [..4]
omit end index = [30, 40, 50] // [2..]

Multi-dimensional array

Can be declared as follows-

let fruits = [["1", "2"],["apple", "orange"]];
println!("Selected fruit is - {}", fruits[1][1]);

Tuples

Tuples are similar to arrays except that tuples can have mixed data types. Similar to arrays tuples are stored in a fiexed-length and the data types must be know at compile time with elements are ordered.

Tuples is declared with comma seperated elements with round braces – (“hello”, 5 , ‘c’)

Here the first element is string then integer and character. See below example how to declare tuples and access elements.

Example-

// declare and inititaize tuple
let tuple = ("Hello", 5 , 's');
// Access elements
println!("First element in tupple is - {}",tuple.0)

Output-

First element in tupple is - Hello

Explict declaration can be done as follows-

Example-

// declare and inititaize tuple
let tuple: (&str, i32, char) = ("Hello", 5 , 's');
// Access elements
println!("First element in tupple is - {}",tuple.0) 
// Prints "First element in tupple is Hello"

Updating element in tuple

First mark the variable as mutable. Access the element of the tuple and update.

// declare and inititaize tuple
let mut tuple: (&str, i32, char)    = ("Hello", 5 , 's');
// Access second element and add 5
tuple.1 += 5;
// Print updated element
println!("Add 5 to second element in tupple - {}",tuple.1)

While updating the element be carefull that the element value does-not exceeds the max value a data type can hold or there will be memory overflow error.

Copy the tuple object

Continuing to the aboce code, decalre the tuple with 3 elements, assign the updated tuple and access the declared variable in tuple.

// declare and inititaize tuple
let mut tuple: (&str, i32, char)    = ("Hello", 5 , 's');
// Access second element and add 5
tuple.1 += 5;
// Print updated element
println!("Add 5 to second element in tupple - {}",tuple.1);

let (first, second , third ) = tuple;
println!("Copied tuple third element is {}", third);

Output-

Add 5 to second element in tupple - 10
Copied tuple third element is s

Warnings-

Above code, first and second element are never used, hence the compiler will give warnings – unused variable:

Although it won’t stop the compiler from running the code. The suggestion here is to use prefix tuple element with _ (underscore) i.e. _first and _second. Lets change this and see if there are no warnings.

    // declare and inititaize tuple
    let mut tuple: (&str, i32, char)    = ("Hello", 5 , 's');
    // Access second element and add 5
    tuple.1 += 5;
    // Print updated element
    println!("Add 5 to second element in tupple - {}",tuple.1);

    let (_first, _second , _third ) = tuple;
    println!("Copied tuple third element is {}", _third);

Now there are no warnings and compiles with results-

Reference

https://doc.rust-lang.org/std/primitive.tuple.html

https://doc.rust-lang.org/rust-by-example/primitives/array.html

Rust Primitive Data types

Last Updated on February 3, 2025 by sandeeppote

Rust variables are immutable by default.

Variables must be explicitly declared as mutable using mut keyword

Rust is a statically typed language – all variable data types must be know at compile time.

Example-

//default immutable. value cannot be changed after declaration
let x = 10; 

// marked as mutable. i.e value can be changed after declaration
let mut y = 20; 

Compiler Errors-

let x = 10;
println!("x is {}", x);
x=20; // Error. Cannot be assigned twice. consider making this muttable
println!("x is {}", x);

Solution-

let mut x = 10; // make this mutable
println!("x is {}", x);
x=20; // compiles successfully
println!("x is {}", x);

Reference

https://doc.rust-lang.org/1.0.0/style/style/naming/README.html

https://rust-lang.github.io/api-guidelines/naming.html

Integer Data Types

Reference https://doc.rust-lang.org/reference/types/numeric.html

  • Unsigned – only represent positive values
  • Signed – represent positive and negative values
  • Characterized by number of bits
LengthSignedUnsigned
8-biti8 ( -(27) to 27-1)u8 ( 0 to 28-1)
16-biti16 ( -(215) to 215-1)u16 ( 0 to 216-1)
32-biti32 ( -(231) to 231-1) defaultu32 ( 0 to 232-1)
64-biti64 ( -(263) to 263-1)u64 ( 0 to 264-1)
128-biti128 ( -(2127) to 2127-1)u128 ( 0 to 2128-1)

Type of the varaible is declared after the : (colon)

Example:-

// signed 8-bit integer. max value can hold is 255
let x: i8 = 255;
let y: i8 = -10;

// unsigned 8-bit integer.
let z: u8 = 255;

Compiler Errors-

// unsigned 8-bit integer. max value 255
let z: u8 = 256;

Solution-

// unsigned 8-bit integer. max value 255
let z: u8 = 255; // compiles successfully

Runtime Errors-

// unsigned 8-bit integer. max value 255
let mut z: u8 = 255;
z = z + 1; // Error: panicked - attempt to add with overflow
println!("z is {}", z);

Solution-

// unsigned 8-bit integer. max value 255
let mut z: u8 = 254;
z = z + 1; // compiles and runs successfully
println!("z is {}", z);

Output- z is 255

Floating-Point Data Types

  • Represent numbers with decimal points
  • f32 and f64 are two floating-point types
  • Value stored as fractional and exponential components

f32- represents value from 6 to 9 decimal digits of precision.

f64- represents value from 15 to 17 decimal digits of precision.

Example-

let x= 10.00; // default is f64
println!("x is {} deafult type is f64", x);

let y: f32= 10.1234567890132456798; // default is f64
println!("y is {} with f32 floating-point type", y);

let z: f64= 10.1234567890132456798; // default is f64
println!("z is {} with f64 floating-point type", z);

Output-

x is 10 deafult type is f64
y is 10.123457 with f32 floating-point type
z is 10.123456789013245 with f64 floating-point type

Guidelines for Numeric data types

Values with fractional component or decimal places use floating-point data type.

Use f64 or been dfault gived most precision range. With modern computers it is as good as using f32. So perrfomance should not be an issue.

Use f32 with embedded systems where memory is a limitation.

Default 32 signed integer (i32) provides a genrous range – between amd aroung plus or minus 2 billion

For memory concerns use smaller size integers to conserve and use less memory

Arithmetic Operations

Rust uses arithmetic operations with the operators +, -, *, / and %

Artihmentic operation results depend on the type of variables. example, if both operators are integer then will get result in integer

let x= 10; // default is i32
let y=3; // default is i32
let z= x / y;
println!("z is {}", z) // so z will be i32

Output- Here the value of z is 3 since both the variables are defaulted to signed integer i.e. i32

z is 3

Now if we add decimals to x and y the output is floating-point-

let x= 10.00; // default is f64
let y=3.00;
let z= x / y;
println!("z is {}", z)

Output- Here the default is f64.

z is 3.3333333333333335

Compiler Errors-

If one of the variables data type is different from other, then will receive error-

let x= 10; // default is i32
let y=3.00; // default is f64s
let z= x / y;
println!("z is {}", z)   

Here the default integer is i32 and floating-point is f64. Dividing different data types will result in error. This is applicable for all artihmetice operations.

Solution-

For the above error cast the variable.

 let x= 10; // default is i32
 let y=3.00; // default is f64s
 let z= x as f64 + y;
 println!("z is {}", z)  

Output-

z is 3.3333333333333335

Formatting print statements

Reference- https://doc.rust-lang.org/std/fmt/

To format the data use Module fmt. This uses the formatting extensions.

Use {} as argument to print the values

Examples-

 println!("Hello {}!", "world"); // prints-  Hello world!
 //named parameters
 println!("{value}", value=10); // prints- 10

 // named paarameters using variable
 let name = "Sandeep Pote";
 println!("Name: {name}");

 // Decimal point upto 3
 let z= 3.33333335;
 println!("z is {:.3}", z);  // prints - 3.333

 // Upto 3 decimal places with lenth of 8 and preceding 0's
 println!("z is {:08.3}", z);  // prints- 0003.333

Output-

Hello world!
10
Name: Sandeep Pote
z is 3.333
z is 0003.333

Positional Parameters

Here the first_name and last_name are named parameters, but the position of printing the parameters are set in different order

println!("{last_name} {first_name}", first_name="Sandeep", last_name="Pote"); //Prints- Pote Sandeep

Binary

Binary trait formats the output as a number in binary

Example-

let value= 0b11110101u8;
println!("value is {}", value)// Prints the number
println!("value is {:b}", value) // prints the binary
println!("value is {:010b}", value) // prints the binary upto 10 digits and preceding 0.

Output-

value is 245
value is 11110101
value is 0011110101

Here the binary is converted to number. The prefix 0b mentions the value is binary and suffix u8 converts the binary to unsigned integer.

Bitwise operations-

Logical operations on patterns using NOT, AND, OR, XOR and SHIFT.

Taking the above example, Bitwise NOT-

let mut value= 0b11110101u8;
value=!value;
println!("value is {:08b}", value); // prints the negated binary

Output-

value is 00001010

Bitwise AND- change the value of a specific Bit-

Use the & with the anotehr binary to change the value.

Example- to change the value of the highlighted 11110111 to 0, & this with 11110011. Ouput will be 11110011

Example-

let mut value= 0b11110111u8;
value=value & 0b11110011;
println!("value is {:08b}", value); 

Output-

value is 11110011

Likewise use | (pipe) for OR, ^ for XOR, << Left shift and >> Right Shift

Boolean data types and operations

Use the above operatos used in bitwise for boolean operations.

Example-

let a = true;
let b= false;
println!("a is {} and b is {}", a, b);
println!("NOT a is {} ", !a);
println!("a AND b is {} ", a & b);
println!("a OR b is {} ", a | b);
println!("a XOR b is {} ", a ^ b);

Output-

a is true and b is false
NOT a is false 
a AND b is false 
a OR b is true 
a XOR b is true 

Short-Circuiting Logical Operations

With this in OR operation if the left side is True then it won’t check the right side since the result for OR will be always true.

Similarly, for AND operation if the left side is False, it won’t check the value at the right side, since the result will be always False.

This can be done using && or ||. This improves the code effeciency.

Example-

let a = true;
let b= false;
let c= (a ^ b) || (a & b);
println!("c is {}", c);

Output-

c is true // (a ^ b) is true || (a & b) is false

Comparision Operations

Reference – https://doc.rust-lang.org/book/appendix-02-operators.html

Use compareision operators to compare values. Some of these are-

  • Equal ==
  • Not Equal !=
  • Greater Than >
  • Less Than <
  • Greater Than Equal >=
  • Less Than Equal <=

Example-

let a = 1;
let b= 2;
println!("a is {} and b is {}", a, b);
println!("a EQUAL TO b is {} ", a == b);
println!("a NOT EQUAL TO b is {} ", a != b);
println!("a GREATER THAN TO b is {} ", a > b);
println!("a LESS THAN TO b is {} ", a < b);
println!("a GREATER THAN EQUAL TO b is {} ", a >= b);
println!("a LESS THAN EQUAL TO b is {} ", a <= b);

Output-

a is 1 and b is 2
a EQUAL TO b is false 
a NOT EQUAL TO b is true 
a GREATER THAN TO b is false 
a LESS THAN TO b is true 
a GREATER THAN EQUAL TO b is false 
a LESS THAN EQUAL TO b is true 

The comparision can be used with the similar data types.

Char Data Type

  • Represents a single character
  • Stored using 4 bytes
  • Unicode scalar value

Char can be represented within a single quote e.g.- ‘a’

Unicode characters can be represented using “\u{hexa decimal value}”

Reference- https://home.unicode.org/

Example-

let letter = 'a';
let number = '1';
let unicode= '\u{0024}';
println!("Letter is {}", letter);
println!("Number is {}", number);
println!("Unicode is {}", unicode);

Output-

Letter is a
Number is 1
Unicode is $

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Sitecore Headless SXA – Create, apply and restrict a custom style to renderings

In this blog post I will show how to apply a custom style to a rendering.

Requirement-

I have a requirement to add extra spacing between the components.

There is already a indent-top style which provides this space (20px) but neesd 100px space.

And the same can see in Experience Editor-

Same can also see in css file in sxastarter project-

Create a custom style (indent-large-top)

Create custom style in Sitecore-

Create a new style (Indent Large Top) in Sitecore under Presentations => Styles ==> Spacing

/sitecore/content/scxmcloud/sxastarter/Presentation/Styles/Spacing

Provide the value of the Style-

Create a style in FE project with the same value-

There are various ways you should be able to do this. I am adding 5 times more space to the existing indent-top style.

_indent.scss

// $middle-margin is defined in _margins.scss
.indent-large-top {
  margin-top: calc($middle-margin * 5);
}

Apply a custom style to rendering

Select the component or container you want to apply style and choose option “Indent Large Top” in Spacing section

Now the space between the 2 component is increased and is 100px as per the requirement.

New style applied to container-

Apply style to specific renderings

As above when the style was created it was applied to all renderings.

If you want to restrict the style to be applied to only certain renderings you can do so by setting Allowed renderings field in new created Style item.

For “Indent Large Top” only SectionContainer will be able to see the new Spacing Style.

In Experience Editor you wont see the “Indent Large Top” for other renderings e.g.- for container rendering-

While for Section Container rendering the new style is available-

References-

https://doc.sitecore.com/xp/en/developers/sxa/103/sitecore-experience-accelerator/add-a-style-for-a-rendering.html

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Guide to avoid scam with crypto

Last Updated on January 21, 2025 by sandeeppote

Keep self-custody of your crypto asset

For Noncustodial wallets keep your recovery code safe

Don’t fall in trap if wallet application asks for recovery code for no reasonRecovery code is asked while creating a wallet i.e. initial setup or if you have lost your wallet i.e. recovery – other than that ensure that you are been not phished

Don’t keep all you crypto assets in a single address

Don’t share the same address to multiple person – Private keys are used to generate the Bitcoin Address. For each transaction create a new address. This way you avoid anybody to know how much bitcoin has been sent to that address in total. Generating new address everytime also protects your privacy.

Block explorer privacy – Block explorer is a web appplication that operates as a Bitcoin search engine. You can search by Bitcoin addresse, transaction hash, block number and block hash. Using these applications and searching a transaction allows them to associate the IP address, previous earches and browser details through which can identify and learn your activities. Searching somebody else transaction should not be a problem but if you search your own transactions these operators might be able to analyse the Bitcoin your have received and spent or currently own. So as mentioned earleir each transaction should be on different address to make the operators difficult to identify you.

Ways to acquire a Bitcoin as a new user

Bitcoin transactions are irreversible. So be careful when doing transaction either send or receive. Since the transactions are done on address and there is not identity attached, there is no verification process to check if the address is your’s before doing a transaction. This way acquring, holding and spending bitcoin does not expose your personal identity. Although everybody in the network can see the how much bitcoin is in a address but that address doesn’t disclose your identity. As a new user follow this guidelines-

  • First do a self study how the crypto transaction works. With most of the mobile apps its as as easy as transfering the fiat currency. But if you have a self custodial assets its very important to understand the process. Understand the current Price of bitcoin from the currency exchange, transaction fees, location from where you will be doing transactions. It is good to understand the rules and regulations of the country where you reside.
  • Get introduction about bitcoin from a friend – Take help from you friend who already has Bitcoin and buy from your them directly with a small amount. This should give you a confidence when doing further transactions by yourself. Once you are familiarised and have confidently done transactions help new users and share your expereince.
  • Earn a bitcoin. Earn a bitcoin by providing service with which ever profession you are in. Example- if you are porgrammer you sell your skills for firat currency, instead sell your service for bitcoin. This requires to share your adddress along with the invoice to your client who should then send agreed bitcoin to your address. This way you learn how to generate address to receive bitcoin. Always remember to genereate new address for each invoice. See section “Don’t share the same address to multiple person“.
  • Use Bitcoin ATM – A Bitcoin ATM is a standalone device or kiosk that allows you to buy or sell bitcoin or other cryptocurrencies using a terminal. Bitcoin ATMs are connected to the Internet and often utilize QR codes to send and receive tokens to users’ digital wallets. Bitcoin ATM accepts cash and send bitcoins to your wallet. This way you get to familiarise with bitcoin transaction’s.
  • Use Bitcoin currency eschange – you can buy bitcoin from the digital curerncy exchange such as Coinbase which is linked to your back account. Although they will take the transaction fees but a safe way to buy or sell the bitcoins.

Generating Private Key

Do not write your own code to create a random number or use a simple random number generator offered by programming language. Use CSPRNG (crytpographically secure pseudorandom number generator) with a seed from a source of sufficient entropy. What is entropy – see here blog post of private key

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How to set background image using Next js in Sitecore XM Cloud

Last Updated on January 8, 2025 by sandeeppote

This is a very common scenario where a background image needs to be set to certain components. Banner’s on any page on your website is a very common place to have a background image.

This blog assumes you have setup the Foundation Head setup or have your own Nextjs project setup implemented using the Sitecore NextJS SDK.

Note: This is not specific to XM Cloud but for any Headless implementation

Foundation Head already has an example on setting the background image using params. In this blog post will explore how this works and where in Sitecore the image can be applied. Will see how this can applied using using OOTB _Background Image item.

To apply image background using rendering parameters to the container see this blog here

Applying background image using rendering field to the components

Background image can be applied to components inheriting the existing __Background Image item to the custom component template.

Create a template for your component. Here I am creating a Banner component-

Inherit _Background Image from /sitecore/templates/Foundation/Experience Accelerator/Presentation/_Background Image

_Background Image has “Background Image” and “Stretch mode” field.

Note that there is a space between the field names, although not recommended but this comes OOTB.

Create a “Banner” JSON Rendering and provide the “Parameters Template”, “Datasource Location” and “Datasource Template” as per your requirement and add this rendering to the “Available Renderings”

Create a Nextjs component in sxastarter project

Note below how the “Background Image” field is set. This is due to the same in field name. Not recommended but this is OOTB.

View this gist on GitHub

Experience Editor-

Add a container component in Main placeholder-

Add a newly created component (Banner) in Container placeholder-

Create or select associated content

Once the component is added you should see the button to Add Background Image ( ths is added when the template inherits from _Background Image template.

Select the Background Image and Save-

You should now able to see the background image to component-

Rendering Host-

Reference-

https://doc.sitecore.com/xmc/en/users/xm-cloud/add-a-background-image.html

First Rust project using cargo package manager

If this is the first time you are using Rust you will have to install Rust on your Windows machine.

To install see this link – https://www.rust-lang.org/tools/install

To install Rust on Windows sybsystem for Linux, use this shell command-

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Check the version of Rust-

rustup --version

Check the version of Rust compiler

rustc --version

To update the Rust, use following command-

rustup update

Create a main.rs file and add code to print a string

fun main(){
    println!("Hello World!")
}

Compile using rust compiler

rustc main.rs

This should create a pdb and exe file

Execute the main.exe file and this should print the string

Create a Rust project using Cargo

Cargo is a build and package manager.

  • Helps to manage dependecies for repetable builds
  • Downloads and builds external libraries
  • calls rustc with correct parameters
  • Included with standard rustup installation

For creating a new Rust project using Cargo package manager-

cargo new first_rust_prj

Tip – The name of the project should be snake case. Example this will give a warning. Atlhough this will create a project.

cargo new FirstRustPrj //Warning
 
Creating binary (application) `FirstRustPrj` package
warning: the name `FirstRustPrj` is not snake_case or kebab-case which is recommended for package names, consider `firstrustprj`

This should create following folder structure with main.rs and Cargo.toml (configuration) file.

TOML – Tom’s Obvoius Minimal Language.

Alternatively, you can create a project without using Cargo. Create a src directory and create appropriate Cargo.toml namually. To create toml file use init command

cargo init

Building and Running Cargo project

Build the Cargo project using following command-

cargo build

To compile and run directly from the project folder, use following command-

cargo run

Error compiling the project-

error: linker link.exe not found

So the pre-requisite for windows machine is to have MS C++ build tools. Install the smae from here. It should be around 5 GB.

https://visualstudio.microsoft.com/visual-cpp-build-tools

Now this should run the project –

To check the code without producing an executable use follwoing command-

cargo check

Building for Release

Use following command when project is ready for release-

cargo build --release

IDE to develop rust-

Visual Studio Code

Install Visual Studio Code. Then install rust-analyzer for code auto completion, hints and code actions – Link

See here the IDE’s the rust analyser supports.

Rust Rover

IDE by Jet Brains – here. This is free for non-commercial users.

References-

https://doc.rust-lang.org/book/ch01-01-installation.html#installing-rustup-on-linux-or-macos

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