Syntax

Rust syntax is concise and explicit. Code lives inside functions, blocks use braces, and most statements end with a semicolon.

Functions and braces

A function is declared with fn. The body goes between curly braces { }.

fn main() {
    println!("Learning Rust syntax");
}

Semicolons

A statement ends with a semicolon ;. The compiler treats lines without a trailing semicolon as expressions, which matters for return values.

fn main() {
    let x = 5;          // statement, ends with ;
    println!("{}", x);  // statement, ends with ;
}

Macros with !

A name followed by ! is a macro, not a function. Macros generate code at compile time and can do things regular functions cannot, like accepting a variable number of arguments.

fn main() {
    println!("A macro");        // prints with a newline
    print!("No newline ");      // prints without a newline
    eprintln!("Error output");  // prints to standard error
}

The {} inside the string is a placeholder filled by the arguments that follow.