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// Copyright © 2024 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::InnerNatural::{Large, Small};
use crate::natural::Natural;
use crate::platform::Limb;
use alloc::vec::Vec;
use malachite_base::num::basic::traits::Zero;
// # Worst-case complexity
// $T(n) = O(n)$
//
// $M(n) = O(1)$
//
// where $T$ is time, $M$ is additional memory, and $n$ is `xs.len()`.
//
// Returns the length of `xs`, excluding trailing zeros.
fn limbs_significant_length(xs: &[Limb]) -> usize {
xs.iter()
.enumerate()
.rev()
.find(|&(_, &x)| x != 0)
.map_or(0, |(i, _)| i + 1)
}
impl Natural {
/// Converts a slice of [limbs](crate#limbs) to a [`Natural`].
///
/// The limbs are in ascending order, so that less-significant limbs have lower indices in the
/// input slice.
///
/// This function borrows the limbs. If taking ownership of limbs is possible,
/// [`from_owned_limbs_asc`](Self::from_owned_limbs_asc) is more efficient.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.len()`.
///
/// This function is more efficient than [`from_limbs_desc`](Self::from_limbs_desc).
///
/// # Examples
/// ```
/// use malachite_base::num::basic::integers::PrimitiveInt;
/// use malachite_nz::natural::Natural;
/// use malachite_nz::platform::Limb;
///
/// if Limb::WIDTH == u32::WIDTH {
/// assert_eq!(Natural::from_limbs_asc(&[]), 0);
/// assert_eq!(Natural::from_limbs_asc(&[123]), 123);
/// // 10^12 = 232 * 2^32 + 3567587328
/// assert_eq!(Natural::from_limbs_asc(&[3567587328, 232]), 1000000000000u64);
/// }
/// ```
pub fn from_limbs_asc(xs: &[Limb]) -> Natural {
let significant_length = limbs_significant_length(xs);
match significant_length {
0 => Natural::ZERO,
1 => Natural(Small(xs[0])),
_ => Natural(Large(xs[..significant_length].to_vec())),
}
}
/// Converts a slice of [limbs](crate#limbs) to a [`Natural`].
///
/// The limbs in descending order, so that less-significant limbs have higher indices in the
/// input slice.
///
/// This function borrows the limbs. If taking ownership of the limbs is possible,
/// [`from_owned_limbs_desc`](Self::from_owned_limbs_desc) is more efficient.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.len()`.
///
/// This function is less efficient than [`from_limbs_asc`](Self::from_limbs_asc).
///
/// # Examples
/// ```
/// use malachite_base::num::basic::integers::PrimitiveInt;
/// use malachite_nz::natural::Natural;
/// use malachite_nz::platform::Limb;
///
/// if Limb::WIDTH == u32::WIDTH {
/// assert_eq!(Natural::from_limbs_desc(&[]), 0);
/// assert_eq!(Natural::from_limbs_desc(&[123]), 123);
/// // 10^12 = 232 * 2^32 + 3567587328
/// assert_eq!(Natural::from_limbs_desc(&[232, 3567587328]), 1000000000000u64);
/// }
/// ```
pub fn from_limbs_desc(xs: &[Limb]) -> Natural {
Natural::from_owned_limbs_asc(xs.iter().cloned().rev().collect())
}
/// Converts a [`Vec`] of [limbs](crate#limbs) to a [`Natural`].
///
/// The limbs are in ascending order, so that less-significant limbs have lower indices in the
/// input [`Vec`].
///
/// This function takes ownership of the limbs. If it's necessary to borrow the limbs instead,
/// use [`from_limbs_asc`](Self::from_limbs_asc).
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.len()`.
///
/// This function is more efficient than [`from_limbs_desc`](Self::from_limbs_desc).
///
/// # Examples
/// ```
/// use malachite_base::num::basic::integers::PrimitiveInt;
/// use malachite_nz::natural::Natural;
/// use malachite_nz::platform::Limb;
///
/// if Limb::WIDTH == u32::WIDTH {
/// assert_eq!(Natural::from_owned_limbs_asc(vec![]), 0);
/// assert_eq!(Natural::from_owned_limbs_asc(vec![123]), 123);
/// // 10^12 = 232 * 2^32 + 3567587328
/// assert_eq!(Natural::from_owned_limbs_asc(vec![3567587328, 232]), 1000000000000u64);
/// }
/// ```
pub fn from_owned_limbs_asc(mut xs: Vec<Limb>) -> Natural {
let significant_length = limbs_significant_length(&xs);
match significant_length {
0 => Natural::ZERO,
1 => Natural(Small(xs[0])),
_ => {
xs.truncate(significant_length);
Natural(Large(xs))
}
}
}
/// Converts a [`Vec`] of [limbs](crate#limbs) to a [`Natural`].
///
/// The limbs are in descending order, so that less-significant limbs have higher indices in the
/// input [`Vec`].
///
/// This function takes ownership of the limbs. If it's necessary to borrow the limbs instead,
/// use [`from_limbs_desc`](Self::from_limbs_desc).
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.len()`.
///
/// This function is less efficient than [`from_limbs_asc`](Self::from_limbs_asc).
///
/// # Examples
/// ```
/// use malachite_base::num::basic::integers::PrimitiveInt;
/// use malachite_nz::natural::Natural;
/// use malachite_nz::platform::Limb;
///
/// if Limb::WIDTH == u32::WIDTH {
/// assert_eq!(Natural::from_owned_limbs_desc(vec![]), 0);
/// assert_eq!(Natural::from_owned_limbs_desc(vec![123]), 123);
/// // 10^12 = 232 * 2^32 + 3567587328
/// assert_eq!(Natural::from_owned_limbs_desc(vec![232, 3567587328]), 1000000000000u64);
/// }
/// ```
pub fn from_owned_limbs_desc(mut xs: Vec<Limb>) -> Natural {
xs.reverse();
Natural::from_owned_limbs_asc(xs)
}
}