1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
// Copyright © 2026 Mikhail Hogrefe
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::natural::Natural;
use crate::natural_polynomial::NaturalPolynomial;
use alloc::vec;
use alloc::vec::Vec;
use malachite_base::num::basic::traits::Zero;
use malachite_base::polynomial::Polynomial;
// Builds p(x^k) coefficient by coefficient, reading the coefficient i/k through `coefficient` where
// k divides i and giving zero elsewhere; for k = 0, sums the coefficients. Nothing is shared with
// the implementation.
pub fn compose_power_of_x_naive(p: &NaturalPolynomial, k: u64) -> NaturalPolynomial {
if k == 0 {
let sum = (0..p.len())
.map(|i| p.coefficient(i).clone())
.sum::<Natural>();
return NaturalPolynomial::from_coefficients_asc(vec![sum]);
}
if p.len() == 0 {
return NaturalPolynomial::ZERO;
}
NaturalPolynomial::from_coefficients_asc(
(0..=(p.len() - 1) * k)
.map(|i| {
if i % k == 0 {
p.coefficient(i / k).clone()
} else {
Natural::ZERO
}
})
.collect::<Vec<Natural>>(),
)
}