Use of macros with parentheses, square brackets, or curly braces

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• In our first example we used the println! macro with parentheses: println!()
• We can also use macros with square brackets and curly braces.
• Macros - the reference

examples/intro/use-macro/src/main.rs

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