comprehensive-rust/src/hello-world.md

# Hello World!

Let us jump into the simplest possible Rust program, a classic Hello World
program:

```rust,editable
fn main() {
    println!("Hello 🌍!");
}
```

What you see:

* Functions are introduced with `fn`.
* Blocks are delimited by curly braces like in C and C++.
* The `main` function is the entry point of the program.
* Rust has hygienic macros, `println!` is an example of this.
* Rust strings are UTF-8 encoded and can contain any Unicode character.

<details>

This slide tries to make the students comfortable with Rust code. They will see
a ton of it over the next four days so we start small with something familiar.

Key points:

* Rust is very much like other languages in the C/C++/Java tradition. It is
  imperative and it doesn't try to reinvent things unless
  absolutely necessary.

* Rust is modern with full support for things like Unicode.

* Rust uses macros for situations where you want to have a variable number of
  arguments (no function [overloading](basic-syntax/functions-interlude.md)).

* Macros being 'hygienic' means they don't accidentally capture identifiers from
  the scope they are used in. Rust macros are actually only
  [partially hygienic](https://veykril.github.io/tlborm/decl-macros/minutiae/hygiene.html).

* Rust is multi-paradigm. For example, it has powerful [object-oriented programming features](https://doc.rust-lang.org/book/ch17-00-oop.html),
  and, while it is not a functional language, it includes a range of [functional concepts](https://doc.rust-lang.org/book/ch13-00-functional-features.html).

</details>