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// 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 malachite_base::num::basic::traits::{One, Two, Zero};
pub fn fibonacci_naive(n: u64) -> Natural {
let (mut a, mut b) = (Natural::ZERO, Natural::ONE);
for _ in 0..n {
let c = &a + &b;
a = b;
b = c;
}
a
}
pub fn fibonacci_pair_naive(n: u64) -> (Natural, Natural) {
if n == 0 {
// F(-1) = 1
return (Natural::ZERO, Natural::ONE);
}
let (mut a, mut b) = (Natural::ZERO, Natural::ONE);
for _ in 1..n {
let c = &a + &b;
a = b;
b = c;
}
(b, a)
}
pub fn lucas_number_naive(n: u64) -> Natural {
let (mut a, mut b) = (Natural::TWO, Natural::ONE);
for _ in 0..n {
let c = &a + &b;
a = b;
b = c;
}
a
}
// The Lucas number pair (L(n), L(n - 1)) is not defined for n == 0, since L(-1) = -1.
pub fn lucas_number_pair_naive(n: u64) -> (Natural, Natural) {
assert_ne!(n, 0);
let (mut a, mut b) = (Natural::TWO, Natural::ONE);
for _ in 1..n {
let c = &a + &b;
a = b;
b = c;
}
(b, a)
}