fn validate_column_degree>()

in prover/src/constraints/evaluation_table.rs [380:413]

• 28 lines of code
• 2 McCabe index (conditional complexity)

fn validate_column_degree<B: StarkField, E: FieldElement<BaseField = B>>(
    column: &[E],
    divisor: &ConstraintDivisor<B>,
    domain_offset: B,
    expected_degree: usize,
) -> Result<(), ProverError> {
    // build domain for divisor evaluation, and evaluate it over this domain
    let g = B::get_root_of_unity(column.len().trailing_zeros());
    let domain = math::get_power_series_with_offset(g, domain_offset, column.len());
    let div_values = domain
        .into_iter()
        .map(|x| E::from(divisor.evaluate_at(x)))
        .collect::<Vec<_>>();

    // divide column values by the divisor
    let mut evaluations = column
        .iter()
        .zip(div_values)
        .map(|(&c, d)| c / d)
        .collect::<Vec<_>>();

    // interpolate evaluations into a polynomial in coefficient form
    let inv_twiddles = fft::get_inv_twiddles::<B>(evaluations.len());
    fft::interpolate_poly_with_offset(&mut evaluations, &inv_twiddles, domain_offset);
    let poly = evaluations;

    if expected_degree != math::polynom::degree_of(&poly) {
        return Err(ProverError::MismatchedConstraintPolynomialDegree(
            expected_degree,
            math::polynom::degree_of(&poly),
        ));
    }
    Ok(())
}