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Using Rust Playground for Hello World and Variable Interpolation

 3 years ago
source link: https://fuzzyblog.io/blog/rust/2020/03/02/using-rust-playground-for-hello-world-and-variable-interpolation.html
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Using Rust Playground for Hello World and Variable Interpolation

Mar 2, 2020

IMG_1313.jpg

Artwork by my friend Autumn Mott; Hopefully I can find a better link to put here

It is a Monday and what better way to start your 6 am Monday morning then learning some of the elements of a new language – Rust.

I started by adding a link in my Browser toolbar to the Rust Playground which amounts to a web based REPL (Read Evaluate Print Loop) for Rust where you can type in Rust code and run it. Yes I know it really isn't a REPL because Rust is a compiled language not an interpreted one but it functions well enough as a REPL that I can wrap my Ruby tinged mind around it.

Here's the Hello World program that automatically appears in the Rust playground

fn main() {
    println!("Hello, world!");
}

The output of this is:

Hello, world!

That's pretty easy to understand:

  • A main function defined with fn
  • A print line function defined with a ! (my previous Rust reading tells me that's a macro indicator)
  • { and } to denote structure
  • A ; to denote the end of lines

I wanted to make a simple change to experiment with the use of variables so I added a main2() function and called it from main():

fn main() {
    println!("Hello, world!");
    main2();
}

fn main2() {
    let x = 5;
    println!("The value of x is: {}", x);
    let y = 6;
    println!("The value of y is: {}", y);
}

The output of this is:

Hello, world!
The value of x is: 5
The value of y is: 6

You can see that the let keyword assigns a variable and that {} binds a variable into a string (which is generally called interpolation).

Note: Variables quickly bring you in to the heart of Rust – immutability – and here there by dragons that hopefully come up tomorrow after some reading.

Here's a permanent link to this if you want to try it out.

What about Repl.it?

Another way to have a web based REPL for Rust is Repl.it. And while I like the concept of repl.it, they have eliminated any privacy without a paid account: Upgrade your account for private repls. This appears on the bottom of every new REPL you create and at $74 / 12 months that feels expensive simply for the basics of privacy.

Posted In: #rust #variables


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