How do I use parameter overloading or optional parameters in rust?

Question

I am trying to write a print function for a binary tree and here is what I have so far:

impl TreeNode {
    fn print(&self) {
        self.print(0);
             


        

Answer 1

Rust does not have overloading, so it is impossible to have two functions or methods with the same name and with different sets of parameters.

However, it is sometimes possible to emulate overload with traits. This approach is likely inappropriate for your use case, but you can see how it is done in the standard library, where Path::new() constructor can be called with something resembling a vector of bytes:

Path::new("/a/b/c/d")   // argument is &str
Path::new(b"/a/b/c/d")  // argument is &[u8]
Path::new(Path::new("/a/b/c/d"))  // argument is another Path

This is done via BytesContainer trait, and new() method is defined like this:

fn new<T: BytesContainer>(bytes: T) -> Path { ... }

Then this trait is implemented for all the types you want:

impl<'a> BytesContainer for &'a str { ... }
impl<'a> BytesContainer for &'a [u8] { ... }
impl BytesContainer for Path { ... }
// and more

This resembles overloading precisely because new() does exactly the same thing regardless of what kind of input it is provided; it is just a convenience thing which makes Path constructor more flexible. In the end new() just converts its argument to a byte slice. However, this does not allow you to have completely different functions with the same name.