Code shared from the Rust Playground

playground.rs

// Ignore this function
fn fused_mul_add(a: [f32; 2], b: [f32; 2], c: [f32; 2]) -> [f32; 2] {
    let mut ret = [0.0, 0.0];
    (0..2).for_each(|i| {
        ret[i] = a[i] * b[i] + c[i];
    });
    ret
}

// I think it should be possible to rewrite this function so that...
fn combined_fused_multiply_add<I>(mut iter: I) -> Option<[f32; 2]>
where
    I: Iterator<Item = ([f32; 2], [f32; 2])>,
{
    iter.next().map(|(a, b)| {
        fused_mul_add(a, b, combined_fused_multiply_add(iter).unwrap_or_default())
    })
}

fn main() {
    let list: Vec<([f32; 2], [f32; 2])> = vec![
        ([0.1, 0.2], [1.1, 1.2]),
        ([0.3, 0.4], [1.3, 1.4]),
        ([0.5, 0.6], [1.3, 1.4]),
    ];

    let res: [f32; 2] = combined_fused_multiply_add(list.into_iter()).unwrap(); // <-- current solution, this works
    // let res: [f32; 2] = list.into_iter().fold(combined_fused_multiply_add.unwrap()); // ...something like this will work?
    dbg!(&res);
}