def reduce

bend-collections-laws-crypto@1.0.0.0 · spec/crypto/aes/poly.bend:65

import Base

65# p(x) modulo m(x) = x^n + low(x), by Horner's rule:
66# p(x) = c + x*q(x), so p mod m = c + x*(q mod m) mod m.
67def reduce(+n: Nat, +low: Word(n), p: List<&2, Bool>) -> Word(n):
68  match p:
69    case Nil{}:
70      Word.zero(n)
71    case c <> q:
72      Word.xor(n, constant(n, c), times_x(n, low, reduce(n, low, q)))