Function compute_one_wave 

fn compute_one_wave(
    i: usize,
    wave: &WaveCode,
    cw_opt: Option<&CompiledWave>,
    needs_init: bool,
    eval: MilkEvaluator,
    left: &[f32],
    right: &[f32],
    spectrum_bins: &[f32],
) -> WaveOutput