Comment by gnuvince

Because of integer overflows and floating-point operations, the notion of equivalent mathematical expressions is tricky.

    fn main() {
        let a: i8 = 125;
        let b: i8 = 3;
        let c: i8 = (a + b) / 2;
        let d: i8 = b + ((a - b) / 2);
        println!("{} {}", c, d);
    }

This program outputs `-64 64` although the computations of `c` and `d` are equivalent.

Here's another example using floating point numbers:

    fn main() {
        let mut total1: f32 = 0.0;
        let mut total2: f32 = 0.0;
        let mut counter1: f32 = 0.0;
        let mut counter2: f32 = 100.0;

        for _ in 0 .. 10001 {
            total1 += counter1;
            total2 += counter2;
            counter1 += 0.01;
            counter2 -= 0.01;
        }
        println!("{} {}", total1, total2);
    }

The output of this program is `500041.16 500012.16`, a difference of 25 for a program that computes the same result (unless I made a mistake).