Rustlings: macros4.rs #Issue79 — Macros in Rust

Rustlings Challenge: macros4.rs Solution Walkthrough

This is the Seventy-ninth (79th) issue of the Rustlings series. In this issue, we provide solutions to Rustlings exercises along with detailed explanations. In this issue we will solve the challenge on macros4.rs.

Previous challenge #Issue 78

Challenge:

// macros4.rs
//
// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
// hint.

// I AM NOT DONE

#[rustfmt::skip]
macro_rules! my_macro {
    () => {
        println!("Check out my macro!");
    }
    ($val:expr) => {
        println!("Look at this other macro: {}", $val);
    }
}

fn main() {
    my_macro!();
    my_macro!(7777);
}

Explanation:

Well this one is a bit tricky and easy at the same time. When we have various macro arms to be matched, we need to add comma after every arm; .

Solution:

#[rustfmt::skip]
macro_rules! my_macro {
    () => {
        println!("Check out my macro!");
    };
    ($val:expr) => {
        println!("Look at this other macro: {}", $val);
    }
}

fn main() {
    my_macro!();
    my_macro!(7777);
}

You can experiment with the code on Rust Playground.

Resources

• Macros
• The Little Book of Rust Macros

Before you go

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Thank you, and we look forward to seeing you for the next challenges!

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