Optional function parameters using macros

---

• Rust does not allow the declaration of the same function-name with different signatures as many other languages.
• Rust does not allow the definition of a function with optional parameters and/or with default values.

• We can use declarative macros to overcome this limitation.

• We could define a macro "only for the case with the optional value" or, as we do in this example, we can create a macro for both cases.

examples/macros/optional-parameter/src/main.rs

// #![feature(trace_macros)]

macro_rules! ping {
    ($address: expr) => {
        ping($address, 4);
    };
    ($address: expr, $repeat: expr) => {
        ping($address, $repeat);
    };
}

fn ping(address: &str, mut repeat: u8) {
    while repeat > 0 {
        println!("ping {address}");
        repeat -= 1;
    }
}
fn main() {
    //    trace_macros!(true);
    ping("localhost", 1);

    //ping("remote");
    ping!("remote");

    ping!("localhost", 3);
    //    trace_macros!(false);
}

ping localhost
ping remote
ping remote
ping remote
ping remote
ping localhost
ping localhost
ping localhost