Learning Rust

Generic function

We will start with a simple generic function squaring a number.

pub fn square<T>(num: T) -> T {
    num * num
}

pub(crate) fn main()
{
    let d = 1.5;
    let e = square(d);
}

Compiler complains that multiplication T * T is not defined and we have to add some type traits.

pub fn square<T>(num: T) -> T where T: Mul<Output = T> + Copy {
    num * num
}

CompilerExplorer

Linter warns that main is not used GitHub issue 12327.

Generic struct

Let us define a generic point class and compare for equality

struct Point<T>
{
    pub x: T,
    pub y: T,
}

fn main()
{
    let p1 = Point{x: 1.2, y:2.3};
    let p2 = Point{x: 1.2, y:2.3};

    assert_eq!(p1 == p2, true);
}

The equality operator can be implemented manually by defining the eq function of the PartialEq trait. For generic structs the impl block also needs an type parameter impl<T> and a type specification, which allows the comparison of the fields.

impl<T: PartialEq> PartialEq for Point<T> {
    fn eq(&self, other: &Self) -> bool {
        self.x == other.x && self.y == other.y
    }
}

CompilerExplorer

It is also possible to generate the operators automatically by using the derive attribute.

#[derive(PartialEq)]
struct Point<T>

CompilerExplorer

Polymorphism

Good article

Machine Learning with ort

https://ort.pyke.io/introduction