Introducing the Rust Crash Course

Originally published by Michael Snoyman at dzone.com

This post is part of a series, Rust Crash Course. You can read all the posts:

In this blog post, I want to explain:

Why I'm interested in Rust.
Why I'm writing up this series.
Who this series is for.
My intended flavor for the series.
Some examples of Rust gotchas I want to cover.

I'm getting to work on this series due to increased Rust usage at FP Complete.

Why Rust?

I'm a strong believer in using the compiler to help eliminate bugs. No programming language can eliminate all bugs and even the best-designed language will typically need to leave developers plenty of wiggle room to shoot themselves in the foot. Still, there's significant value in safety and long-term maintainability of projects that use languages with this focus.

For about ten years now, my primary language has been (and continues to be) Haskell. It gets a lot of things right here, such as immutability, explicit effects, and strong typing. But I've got two problems with an intense focus on Haskell:

There's always something to be learned from other languages. It's quite easy to fall into the trap of knowing one language well and becoming blind to its shortcomings. Haskell is now the language I've used for the longest stretch of time as a primary language, finally displacing Java. I need to avoid this trap.
There are some legitimate technical advantages of Rust:
Performance is better, and more reliable as well, relying less upon things like rewrite rules firing.
It's got a better story right now for mobile and front-end development.
Lack of garbage collection opens up new possibilities in real-time development.
Rust improves on Haskell's safety guarantees in some places, such as defaulting to requiring complete pattern matches.

Like many others, I've been hearing a buzz around Rust for years. Two or so years ago, I started playing around with it more, and have been steadily dedicating more personal time to it. But recently, we've had more Rust interest at work, and therefore we've been expanding our internal Rust team.

Why This Series?

We're a globally distributed team at FP Complete, and we make a heavy push towards using written communication tools wherever possible. This also overlaps heavily with training material. As I do more training (both internally, and for customers), I'm discovering places where:

I'm finding my own knowledge of the language was lacking.
Newcomers are stumbling hard.

This series is intended to collect both initial pointers of how to get started with Rust and hard-learned lessons of how to avoid getting stuck. Some of these stumbling blocks may favor the kind of audience I'm working with directly (lots of Haskell and DevOps engineers), but that will likely change over time.

Target Audience

I'm gearing this series towards the Rust curious. I'm assuming programming knowledge, and some basic idea of what Rust is about, but no real knowledge of the language itself. I'll try to call out when you should go read the Rust book.

If you're a Java user, a Rubyist, or a Haskeller, and Rust intrigues you, I hope this will help you. And maybe even Rustaceans will enjoy seeing the pain points I find myself and others are hitting.

Flavor of the Series

There is already really good material on Rust available from rust-lang.org. I have no intention of trying to replace that. Instead, I'll assume that people are reading through the Rust book, and point to sections where appropriate.

One concrete example: I don't intend to spend a lot of time talking about Rust syntax, or explaining that it's an expression-oriented language. The book covers that.

Instead, I want to give people:

Real code to look at and play with.
Simple problems to build up experience with.
Explanations of tricky cases that catch people up.

And on that note...

Rust Gotchas

A few people on Twitter asked me to share some Rust gotchas, especially coming from the perspective of a Haskell developer. I'll certainly be covering more gotchas going forward, but I wanted to give some examples in this first post so you can get a feel for the kinds of things we'll be addressing in the series. I'm not going to be explaining details of these problems here; that's what the series is for!

Just so you know: there's no content following these examples, besides the Disqus comments below. If you're not interested in the gotchas, feel free to quit reading now and stay tuned for more posts.

Mutable Values, Mutable Variables

I've got a simple mental model in Haskell. Values are all immutable, period. A few special reference types allow me to mutate their contents. And mutating like that is an effect tracked in the type system.

From that perspective, Rust is a bit surprising. Here's one:

fn main() {
    let i: isize = 1;
    let j: isize = foo(i);
    println!("{}", j);
}
fn foo(mut i: isize) -> isize {
    i += 1;
    i
}

Wait a second... i is immutable. Then I pass it to foo, and it becomes mutable. Then I return this mutable value as an immutable value. What?

I assure you, this ultimately makes sense, but it's kind of surprising. Also, the fact that x: &mut isize and mut x: &mut isize are both real things that mean different things:

fn main() {
    let mut i: isize = 1;
    let mut j: isize = 2;
    foo(&mut i, &mut j);
    println!("{} {}", i, j);
}
fn foo<'a>(mut i: &'a mut isize, j: &'a mut isize) {
    *i *= 10;
    i = j;
    *i *= 10;
}

So Many Strings

I was warned about this one and blew it off. I thought to myself, 'there's no way a Haskeller, trained in the arts of String, strict Text, lazy Text, ByteString s and more could be daunted.' I was wrong.

fn main() {
    let hello1 = String::from("Hello, ");
    let hello2 = String::from(", hello!");
    let name = "Alice";
    println!("{}", hello1 + name);
    println!("{}", name + hello2);
}

Nope, the code above doesn't compile.

Magically Works, Until it Doesn't

There are a number of "magic" things that happen in Rust in the name of ergonomics. Often, they work perfectly and save a lot of frustration. And sometimes, they fail. Look at this broken code:

fn main() {
    for arg in std::env::args().skip(1) {
        respond(arg);
    }
}
fn respond(arg: &str) {
    match arg {
        "hi" => println!("Hello there!"),
        "bye" => println!("OK, goodbye!"),
        _ => println!("Sorry, I don't know what {} means", arg),
    }
}

You'll get an error message:

expected &str, found struct `std::string::String`

Oh, well that makes sense! I need to get a reference to a str instead of the String I got from args(). Easy enough to fix:

respond(&arg);

But then I realize that the respond function is silly and inline the match:

fn main() {
    for arg in std::env::args().skip(1) {
        match &arg {
            "hi" => println!("Hello there!"),
            "bye" => println!("OK, goodbye!"),
            _ => println!("Sorry, I don't know what {} means", arg),
        }
    }
}

I remembered to match on &arg instead of arg, so you'd think it would be fine. But it isn't:

 |             ^^^^ expected struct `std::string::String`, found str
  |
  = note: expected type `&std::string::String`
             found type `&'static str`

Huh, that's weird. In order to figure out what's going on here, you have to understand quite a few details of the deref magic going on behind the scenes. I dare say some of this magic is even a leaky abstraction (don't worry, it's still zero cost). You can solve this with either:

match &*arg {

or

match arg.as_ref() {

Moving Data Into Closures

The biggest pain points I've encountered so far in my Rust odyssey are all around moving data into closures. I've been spoiled by Haskell: I like to use closures constantly, and am used to garbage collection just letting it all magically work.

I've got some real head-scratchers to demonstrate later, but have fun with this relatively simple example:

fn main() {
    let hello = String::from("Hello, ");
    let greet = |name| hello + name;
    println!("{}", greet("Alice"));
    println!("{}", greet("Bob"));
}

Originally published by Michael Snoyman at dzone.com

========================================

Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on Facebook | Twitter

Learn More

☞ The Rust Programming Language

☞ Rust: Building Reusable Code with Rust from Scratch

☞ Programming in Rust: the good, the bad, the ugly.

☞ An introduction to Web Development with Rust for Node.js Developers

#rust #web-development

What is GEEK

Buddha Community

Sival Alethea

1624395600

MongoDB with Python Crash Course - Tutorial for Beginners. DO NOT MISS!!!

Learn the most popular NoSQL / document database: MongoDB. In this quickstart tutorial, you’ll be up and running with MongoDB and Python.
⭐️Course Contents⭐️
⌨️ (0:00:00) Welcome
⌨️ (0:04:33) Intro to MongoDB
⌨️ (0:07:49) How do document DBs work?
⌨️ (0:10:34) Who uses MongoDB
⌨️ (0:13:02) Data modeling
⌨️ (0:16:30) Modeling guidelines
⌨️ (0:22:11) Integration database
⌨️ (0:24:23) Getting demo code
⌨️ (0:30:07) How ODMs work?
⌨️ (0:32:55) Introduction to mongoengine
⌨️ (0:34:01) Demo: Registering connections with MongoEngine
⌨️ (0:37:20) Concept: Registering connections
⌨️ (0:39:14) Demo: Defining mongoengine entities (classes)
⌨️ (0:45:22) Concept: mongoengine entities
⌨️ (0:49:03) Demo: Create a new account
⌨️ (0:56:55) Demo: Robo 3T for viewing and managing data
⌨️ (0:58:18) Demo: Login
⌨️ (1:00:07) Demo: Register a cage
⌨️ (1:10:28) Demo: Add a bookable time as a host
⌨️ (1:16:13) Demo: Managing your snakes as a guest
⌨️ (1:19:18) Demo: Book a cage as a guest
⌨️ (1:33:41) Demo: View your bookings as guest
⌨️ (1:41:29) Demo: View bookings as host
⌨️ (1:46:18) Concept: Inserting documents
⌨️ (1:47:28) Concept: Queries
⌨️ (1:48:09) Concept: Querying subdocuments with mongoengine
⌨️ (1:49:37) Concept: Query using operators
⌨️ (1:50:24) Concept: Updating via whole documents
⌨️ (1:51:46) Concept: Updating via in-place operators
⌨️ (1:54:01) Conclusion

📺 The video in this post was made by freeCodeCamp.org
The origin of the article: https://www.youtube.com/watch?v=E-1xI85Zog8&list=PLWKjhJtqVAbnqBxcdjVGgT3uVR10bzTEB&index=10
🔥 If you’re a beginner. I believe the article below will be useful to you ☞ What You Should Know Before Investing in Cryptocurrency - For Beginner
⭐ ⭐ ⭐The project is of interest to the community. Join to Get free ‘GEEK coin’ (GEEKCASH coin)!
☞ **-----CLICK HERE-----**⭐ ⭐ ⭐
Thanks for visiting and watching! Please don’t forget to leave a like, comment and share!

#mongodb #python #python crash course #mongodb with python crash course - tutorial for beginners #beginners #mongodb with python crash course

Heloise Schuster

1629837300

Rust Lang Course For Beginner In 2021: Guessing Game

What we learn in this chapter:
- Rust number types and their default
- First exposure to #Rust modules and the std::io module to read input from the terminal
- Rust Variable Shadowing
- Rust Loop keyword
- Rust if/else
- First exposure to #Rust match keyword

=== Content:
00:00 - Intro & Setup
02:11 - The Plan
03:04 - Variable Secret
04:03 - Number Types
05:45 - Mutability recap
06:22 - Ask the user
07:45 - First intro to module std::io
08:29 - Rust naming conventions
09:22 - Read user input io:stdin().read_line(&mut guess)
12:46 - Break & Understand
14:20 - Parse string to number
17:10 - Variable Shadowing
18:46 - If / Else - You Win, You Loose
19:28 - Loop
20:38 - Match
23:19 - Random with rand
26:35 - Run it all
27:09 - Conclusion and next episode

#rust

Genevieve Prohaska

1591267050

Flask Crash Course For Beginners [Python Web Development]

Welcome to Flask Crash Course For Beginners [Python Web Development], in this video we are going to talk about about different concepts in flask. so as you k…

#python #flask crash course #flask #crash course #progaming

vrushanjali thippabathula

1593242571

Techtutorials | Online IT Courses, Training, Syllabus

Techtutorials tell you the best online IT courses/training, tutorials, certification courses, and syllabus from beginners to advanced level on the latest technologies recommended by Programming Community through video-based, book, free, paid, Real-time Experience, etc.

#techtutorials #online it courses #mobile app development courses #web development courses #online courses for beginners #advanced online courses

Karim Aya

1564915178