A simple question about interpolate

[eigmax]

When testing FFT, I try to interpolate a trace points and then evaluate as below.

        let points: Vec<u32> = (1..=4).collect();;
        let mut a: Vec<BaseElement> = points.iter().map(|e| BaseElement::from(e.clone()) ).collect();

        let inv_twiddles = get_inv_twiddles::<BaseElement>(points.len());
        println!("{:?}", points);
        fft::interpolate_poly(&mut a, &inv_twiddles);
        fft::evaluate_poly(&mut a, &inv_twiddles);
        
        let res : Vec<_> = a.iter().map(|e| { e.as_int() }).collect();
        println!("post {:?}", res);

output:

prev:   1, 2, 3, 4
post:   1, 4, 3, 2

I expect that the post suppose to be as same as the prev. Can you please help to explain how this happen?

[eigmax]

eval should use twiddles. close.