Ah, yes! A classic "Hello world!" example. This one will be really quick, but I'll show you an important difference between Node and Rust.
Create a hello-world.js containing nothing more than this line:
console.log('Hello world!');And now run this file with Node:
$ node hello-word.js
Hello world!Yeah! You'll see Hello world! in your console.
Now we'll do the same for Rust. Create a hello_world.rs with the following content:
fn main() {
println!("Hello world!");
}Rust actually needs a special entry point to execute code. This is our main function and as you can see a function in Rust is declared like in JavaScript, but with the fn keyword instead of function. It is important to call the function main or the Rust compiler will throw an error. In Rust we typically use 4 spaces to indent code inside a function, while 2 spaces are more common for JavaScript projects. (But thankfully this is covered by prettier anyway and it could be covered by rustfmt when my feature request will be solved.) Rust also recommends snake_case naming style for directories and files while I think kebab-case is most common in JavaScript projects. println isn't a simple function call, but a macro - which is indicated by the !. For now think of a macro as some code which is transformed into other code at compile time. Last but not least you need to wrap your string inside ", not '. In JavaScript there is no difference between " and ' to create strings (and many prefer to use ', even though it's not prettiers default). In Rust a " creates a string literal while ' creates a character literal which means it only accepts a single character. You could write println!("H"); or println!('H'); and both would compile, but println!('Hello World!'); throws an error.
Now compile our code with the following command:
$ rustc hello_world.rsYou'll see... nothing on your console. Instead a new file called hello_world was created next to hello_world.rs. This file contains our compiled code. You can run it like this:
$ ./hello-world
Hello world!Now you'll see Hello world! in your console. This shows a fundamental difference between JavaScript/Node and Rust. Rust needs to be compiled before our program can be executed. This extra step is not needed for JavaScript which makes the development cycle with JavaScript sometimes faster. However the compilation step catches a ton of bugs before even executing your program. This can be so useful that you probably want to introduce a similar sanity check to JavaScript - for example by using TypeScript. There is another big benefit: we can easily share our compiled hello-world program with other developers without the need for them to have Rust installed. This is not possible with Node scripts. Everyone who wants to run our hello-world.js needs to have Node installed and in a version which is supported by our script.
In the next chapter I'll introduce you to package managing. I choose to talk about this topic, because it is the last topic related to "project configuration" before we can actually focus on small programming examples to learn the language itself.