fact: Definition step m n w (p : {poly R}) := \sum_(l < 2 ^ m) let ev := \poly_(i < 2 ^ n) p`_(i + l * 2 ^ n.+1) in let ov := \poly_(i < 2 ^ n) p`_(i + l * 2 ^ n.+1 + 2 ^ n) in \sum_(j < 2 ^ n) ((ev`_j + ov`_ j * w ^+ j) *: 'X^(j + l * 2 ^ n.+1) + (ev`_j - ov`_ j * w ^+ j) *: 'X^(j + l * 2 ^ n.+1 + 2 ^ n)).
imports: mathcomp(all_ssreflect all_algebra ssrnum) digitn