The Rust Programming Language - Understanding Structs in Rust

structs are a way of creating more complex data types. For example, if we were doing calculations involving coordinates in 2D space, we would need both an x and a y value:


# #![allow(unused_variables)]
#fn main() {
let origin_x = 0;
let origin_y = 0;
#}

A struct lets us combine these two into a single, unified datatype with x and y as field labels:

struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let origin = Point { x: 0, y: 0 }; // origin: Point

    println!("The origin is at ({}, {})", origin.x, origin.y);
}

There’s a lot going on here, so let’s break it down. We declare a struct with the struct keyword, and then with a name. By convention, structs begin with a capital letter and are camel cased: PointInSpace, not Point_In_Space.

We can create an instance of our struct via let, as usual, but we use a key: value style syntax to set each field. The order doesn’t need to be the same as in the original declaration.

Finally, because fields have names, we can access them through dot notation: origin.x.

The values in structs are immutable by default, like other bindings in Rust. Use mut to make them mutable:

struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let mut point = Point { x: 0, y: 0 };

    point.x = 5;

    println!("The point is at ({}, {})", point.x, point.y);
}

This will print The point is at (5, 0).

Rust does not support field mutability at the language level, so you cannot write something like this:

struct Point {
    mut x: i32, // This causes an error.
    y: i32,
}

Mutability is a property of the binding, not of the structure itself. If you’re used to field-level mutability, this may seem strange at first, but it significantly simplifies things. It even lets you make things mutable on a temporary basis:

struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let mut point = Point { x: 0, y: 0 };

    point.x = 5;

    let point = point; // `point` is now immutable.

    point.y = 6; // This causes an error.
}

Your structure can still contain &mut references, which will let you do some kinds of mutation:

struct Point {
    x: i32,
    y: i32,
}

struct PointRef<'a> {
    x: &'a mut i32,
    y: &'a mut i32,
}

fn main() {
    let mut point = Point { x: 0, y: 0 };

    {
        let r = PointRef { x: &mut point.x, y: &mut point.y };

        *r.x = 5;
        *r.y = 6;
    }

    assert_eq!(5, point.x);
    assert_eq!(6, point.y);
}

Initialization of a data structure (struct, enum, union) can be simplified when fields of the data structure are initialized with variables of the same names as the fields.

#[derive(Debug)]
struct Person<'a> {
    name: &'a str,
    age: u8
}

fn main() {
    // Create struct with field init shorthand
    let name = "Peter";
    let age = 27;
    let peter = Person { name, age };

    // Debug-print struct
    println!("{:?}", peter);
}

Update syntax

A struct can include .. to indicate that you want to use a copy of some other struct for some of the values. For example:


# #![allow(unused_variables)]
#fn main() {
struct Point3d {
    x: i32,
    y: i32,
    z: i32,
}

let mut point = Point3d { x: 0, y: 0, z: 0 };
point = Point3d { y: 1, .. point };
#}

This gives point a new y, but keeps the old x and z values. It doesn’t have to be the same struct either, you can use this syntax when making new ones, and it will copy the values you don’t specify:


# #![allow(unused_variables)]
#fn main() {
# struct Point3d {
#     x: i32,
#     y: i32,
#     z: i32,
# }
let origin = Point3d { x: 0, y: 0, z: 0 };
let point = Point3d { z: 1, x: 2, .. origin };
#}

Tuple structs

Rust has another data type that’s like a hybrid between a tuple and a struct, called a ‘tuple struct’. Tuple structs have a name, but their fields don’t. They are declared with the struct keyword, and then with a name followed by a tuple:


# #![allow(unused_variables)]
#fn main() {
struct Color(i32, i32, i32);
struct Point(i32, i32, i32);

let black = Color(0, 0, 0);
let origin = Point(0, 0, 0);
#}

Here, black and origin are not the same type, even though they contain the same values.

The members of a tuple struct may be accessed by dot notation or destructuring let, just like regular tuples:


# #![allow(unused_variables)]
#fn main() {
# struct Color(i32, i32, i32);
# struct Point(i32, i32, i32);
# let black = Color(0, 0, 0);
# let origin = Point(0, 0, 0);
let black_r = black.0;
let Point(_, origin_y, origin_z) = origin;
#}

Patterns like Point(_, origin_y, origin_z) are also used in match expressions.

One case when a tuple struct is very useful is when it has only one element. We call this the ‘newtype’ pattern, because it allows you to create a new type that is distinct from its contained value and also expresses its own semantic meaning:


# #![allow(unused_variables)]
#fn main() {
struct Inches(i32);

let length = Inches(10);

let Inches(integer_length) = length;
println!("length is {} inches", integer_length);
#}

As above, you can extract the inner integer type through a destructuring let. In this case, the let Inches(integer_length) assigns 10 to integer_length. We could have used dot notation to do the same thing:


# #![allow(unused_variables)]
#fn main() {
# struct Inches(i32);
# let length = Inches(10);
let integer_length = length.0;
#}

It’s always possible to use a struct instead of a tuple struct, and can be clearer. We could write Color and Point like this instead:


# #![allow(unused_variables)]
#fn main() {
struct Color {
    red: i32,
    blue: i32,
    green: i32,
}

struct Point {
    x: i32,
    y: i32,
    z: i32,
}
#}

Good names are important, and while values in a tuple struct can be referenced with dot notation as well, a struct gives us actual names, rather than positions.

Unit-like structs

You can define a struct with no members at all:

struct Electron {} // Use empty braces...
struct Proton;     // ...or just a semicolon.

// Use the same notation when creating an instance.
let x = Electron {};
let y = Proton;
let z = Electron; // Error

Such a struct is called ‘unit-like’ because it resembles the empty tuple, (), sometimes called ‘unit’. Like a tuple struct, it defines a new type.

This is rarely useful on its own (although sometimes it can serve as a marker type), but in combination with other features, it can become useful. For instance, a library may ask you to create a structure that implements a certain trait to handle events. If you don’t have any data you need to store in the structure, you can create a unit-like struct.

#Rust #WebDev

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Buddha Community

The Rust Programming Language - Understanding Structs in Rust

Genesis Prosacco

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RUST on programming language

The title is a bit confusing to understand the context of the content. In this blog, I am going to run around and see the different aspects of programming language rust. And talk about the concepts that it introduces that are useful for various aspects of programming.

What is Rust?

Simply putting it is a statically as well as strongly typed programming language.

Let me explain:

_statically typed _indicates that all the datatypes that are expressed in the code are known at compile time and memory allocation is done properly.

Image for post

Then what is 👆 that? Let’s just say rust knows what you want to say.

But this doesn’t mean you could declare variables for a complex data type and expect rust to understand. Here comes the next point I mentioned above.

_strongly typed _indicates that the types are designed to make it harder to write syntatically incorrect code.

If you were to do even a little mistake with the syntax or definition of variables then the errors are caught at compile time. Not just the syntax errors but there are various tests build in the compiler to check for unused variables, dead code(Code that will never run), infinite loops as well as the lifetime of variables.

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Serde Rust: Serialization Framework for Rust

Serde

*Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.*

You may be looking for:

Serde in action

Click to show Cargo.toml. Run this code in the playground.

[dependencies]

# The core APIs, including the Serialize and Deserialize traits. Always
# required when using Serde. The "derive" feature is only required when
# using #[derive(Serialize, Deserialize)] to make Serde work with structs
# and enums defined in your crate.
serde = { version = "1.0", features = ["derive"] }

# Each data format lives in its own crate; the sample code below uses JSON
# but you may be using a different one.
serde_json = "1.0"

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point { x: 1, y: 2 };

    // Convert the Point to a JSON string.
    let serialized = serde_json::to_string(&point).unwrap();

    // Prints serialized = {"x":1,"y":2}
    println!("serialized = {}", serialized);

    // Convert the JSON string back to a Point.
    let deserialized: Point = serde_json::from_str(&serialized).unwrap();

    // Prints deserialized = Point { x: 1, y: 2 }
    println!("deserialized = {:?}", deserialized);
}

Getting help

Serde is one of the most widely used Rust libraries so any place that Rustaceans congregate will be able to help you out. For chat, consider trying the #rust-questions or #rust-beginners channels of the unofficial community Discord (invite: https://discord.gg/rust-lang-community), the #rust-usage or #beginners channels of the official Rust Project Discord (invite: https://discord.gg/rust-lang), or the #general stream in Zulip. For asynchronous, consider the [rust] tag on StackOverflow, the /r/rust subreddit which has a pinned weekly easy questions post, or the Rust Discourse forum. It's acceptable to file a support issue in this repo but they tend not to get as many eyes as any of the above and may get closed without a response after some time.

Download Details:
Author: serde-rs
Source Code: https://github.com/serde-rs/serde
License: View license

#rust #rustlang

Cayla Erdman

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Introduction to Structured Query Language SQL pdf

SQL stands for Structured Query Language. SQL is a scripting language expected to store, control, and inquiry information put away in social databases. The main manifestation of SQL showed up in 1974, when a gathering in IBM built up the principal model of a social database. The primary business social database was discharged by Relational Software later turning out to be Oracle.

Models for SQL exist. In any case, the SQL that can be utilized on every last one of the major RDBMS today is in various flavors. This is because of two reasons:

1. The SQL order standard is genuinely intricate, and it isn’t handy to actualize the whole standard.

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Right now, contrasts are noted where fitting.

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Guide to Python Programming Language

Description
The course will lead you from beginning level to advance in Python Programming Language. You do not need any prior knowledge on Python or any programming language or even programming to join the course and become an expert on the topic.

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#uide to Python #Guide to Python Programming #Guide to Python Programming Language #Python Programming #Python Programming Language

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OS in Rust: An executable that runs on bare metal

This is the very first blog of the series that pertains to create a basic Operating System using Rust Programming Language.

The aim of this series is to learn and understand the basics of Operating System. Through this series, you will get some ideas about the internal components of Operating System and how they interact with each other.

In this article, we will create a freestanding binary (an executable) that has the capability to run on bare metal. To create that executable we need to follow certain steps:

Steps to create a bare-metal executable:

Disable standard library
Define custom panic handler
Provide language items
Provide entry point
Build executable

#functional programming #rust #rust programming language #system programming