Arithmetic

fn interproduct(a: i32, b: i32, c: i32) -> i32 {
    return a * b + b * c + c * a;
}
fn main() {
    println!("result: {}", interproduct(120, 100, 248));
}

This slide should take about 3 minutes.

This is the first time we’ve seen a function other than main, but the meaning should be clear: it takes three integers, and returns an integer. Functions will be covered in more detail later.

Arithmetic is very similar to other languages, with similar precedence.

What about integer overflow? In C and C++ overflow of signed integers is actually undefined, and might do unknown things at runtime. In Rust, it’s defined.

Change the i32‘s to i16 to see an integer overflow, which panics (checked) in a debug build and wraps in a release build. There are other options, such as overflowing, saturating, and carrying. These are accessed with method syntax, e.g., (a * b).saturating_add(b * c).saturating_add(c * a).

In fact, the compiler will detect overflow of constant expressions, which is why the example requires a separate function.