Defining tuple methods

Question

Here's a swap function for two-element tuples:

fn swap<A, B>(obj: (A, B)) -> (B, A)
{
    let (a, b) = obj;

    (b, a)
}

Example use:

fn main() {
    let obj = (10i, 20i);

    println!("{}", swap(obj));
}

Is there a way to define swap as a method on two-element tuples? I.e. so that it may be called like:

(10i, 20i).swap()

Vladimir Matveev · Accepted Answer · 2014-10-10 17:49:27Z

7

Yes, there is. Just define a new trait and implement it immediately, something like this:

trait Swap<U> {
    fn swap(self) -> U;
}

impl<A, B> Swap<(B, A)> for (A, B) {
    #[inline]
    fn swap(self) -> (B, A) {
        let (a, b) = self;
        (b, a)
    }
}

fn main() {
    let t = (1u, 2u);
    println!("{}", t.swap());
}

Note that in order to use this method you will have to import Swap trait into every module where you want to call the method.

answered Oct 10, 2014 at 17:49

Vladimir Matveev

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