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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 core::cmp::Ordering::{self, *};
use core::ops::{Shl, ShlAssign};
use malachite_base::num::arithmetic::traits::{
ShlRound, ShlRoundAssign, ShrRound, ShrRoundAssign, UnsignedAbs,
};
use malachite_base::num::basic::signeds::PrimitiveSigned;
use malachite_base::rounding_modes::RoundingMode;
fn shl_round_ref<'a, U, S: PrimitiveSigned + UnsignedAbs<Output = U>>(
x: &'a Natural,
bits: S,
rm: RoundingMode,
) -> (Natural, Ordering)
where
&'a Natural: Shl<U, Output = Natural> + ShrRound<U, Output = Natural>,
{
if bits >= S::ZERO {
(x << bits.unsigned_abs(), Equal)
} else {
x.shr_round(bits.unsigned_abs(), rm)
}
}
fn shl_round_assign_n<U, S: PrimitiveSigned + UnsignedAbs<Output = U>>(
x: &mut Natural,
bits: S,
rm: RoundingMode,
) -> Ordering
where
Natural: ShlAssign<U> + ShrRoundAssign<U>,
{
if bits >= S::ZERO {
*x <<= bits.unsigned_abs();
Equal
} else {
x.shr_round_assign(bits.unsigned_abs(), rm)
}
}
macro_rules! impl_natural_shl_round_signed {
($t:ident) => {
impl ShlRound<$t> for Natural {
type Output = Natural;
/// Left-shifts a [`Natural`] (multiplies or divides it by a power of 2), taking it by
/// value, and rounds according to the specified rounding mode. An [`Ordering`] is also
/// returned, indicating whether the returned value is less than, equal to, or greater
/// than the exact value. If `bits` is non-negative, then the returned [`Ordering`] is
/// always `Equal`, even if the higher bits of the result are lost.
///
/// Passing `Floor` or `Down` is equivalent to using `>>`. To test whether `Exact` can
/// be passed, use `bits > 0 || self.divisible_by_power_of_2(bits)`. Rounding might only
/// be necessary if `bits` is negative.
///
/// Let $q = x2^k$, and let $g$ be the function that just returns the first element of
/// the pair, without the [`Ordering`]:
///
/// $g(x, k, \mathrm{Down}) = g(x, y, \mathrm{Floor}) = \lfloor q \rfloor.$
///
/// $g(x, k, \mathrm{Up}) = g(x, y, \mathrm{Ceiling}) = \lceil q \rceil.$
///
/// $$
/// f(x, k, \mathrm{Nearest}) = \begin{cases}
/// \lfloor q \rfloor & \text{if}
/// \\quad q - \lfloor q \rfloor < \frac{1}{2}, \\\\
/// \lceil q \rceil & \text{if}
/// \\quad q - \lfloor q \rfloor > \frac{1}{2}, \\\\
/// \lfloor q \rfloor & \text{if} \\quad q - \lfloor q \rfloor =
/// \frac{1}{2} \\ \text{and} \\ \lfloor q \rfloor
/// \\ \text{is even}, \\\\
/// \lceil q \rceil &
/// \text{if} \\quad q - \lfloor q \rfloor = \frac{1}{2} \\ \text{and}
/// \\ \lfloor q \rfloor \\ \text{is odd}.
/// \end{cases}
/// $$
///
/// $g(x, k, \mathrm{Exact}) = q$, but panics if $q \notin \N$.
///
/// Then
///
/// $f(x, k, r) = (g(x, k, r), \operatorname{cmp}(g(x, k, r), q))$.
///
/// # Worst-case complexity
/// $T(n, m) = O(n + m)$
///
/// $M(n, m) = O(n + m)$
///
/// where $T$ is time, $M$ is additional memory, $n$ is `self.significant_bits()`, and
/// $m$ is `max(bits, 0)`.
///
/// # Panics
/// Let $k$ be `bits`. Panics if $k$ is negative and `rm` is `Exact` but `self` is not
/// divisible by $2^{-k}$.
///
/// # Examples
/// See [here](super::shl_round#shl_round).
#[inline]
fn shl_round(mut self, bits: $t, rm: RoundingMode) -> (Natural, Ordering) {
let o = self.shl_round_assign(bits, rm);
(self, o)
}
}
impl ShlRound<$t> for &Natural {
type Output = Natural;
/// Left-shifts a [`Natural`] (multiplies or divides it by a power of 2), taking it by
/// reference, and rounds according to the specified rounding mode. An [`Ordering`] is
/// also returned, indicating whether the returned value is less than, equal to, or
/// greater than the exact value. If `bits` is non-negative, then the returned
/// [`Ordering`] is always `Equal`, even if the higher bits of the result are lost.
///
/// Passing `Floor` or `Down` is equivalent to using `>>`. To test whether `Exact` can
/// be passed, use `bits > 0 || self.divisible_by_power_of_2(bits)`. Rounding might only
/// be necessary if `bits` is negative.
///
/// Let $q = x2^k$, and let $g$ be the function that just returns the first element of
/// the pair, without the [`Ordering`]:
///
/// $g(x, k, \mathrm{Down}) = g(x, y, \mathrm{Floor}) = \lfloor q \rfloor.$
///
/// $g(x, k, \mathrm{Up}) = g(x, y, \mathrm{Ceiling}) = \lceil q \rceil.$
///
/// $$
/// g(x, k, \mathrm{Nearest}) = \begin{cases}
/// \lfloor q \rfloor & \text{if}
/// \\quad q - \lfloor q \rfloor < \frac{1}{2}, \\\\
/// \lceil q \rceil & \text{if}
/// \\quad q - \lfloor q \rfloor > \frac{1}{2}, \\\\
/// \lfloor q \rfloor & \text{if} \\quad q - \lfloor q \rfloor =
/// \frac{1}{2} \\ \text{and} \\ \lfloor q \rfloor
/// \\ \text{is even}, \\\\
/// \lceil q \rceil &
/// \text{if} \\quad q - \lfloor q \rfloor = \frac{1}{2} \\ \text{and}
/// \\ \lfloor q \rfloor \\ \text{is odd}.
/// \end{cases}
/// $$
///
/// $g(x, k, \mathrm{Exact}) = q$, but panics if $q \notin \N$.
///
/// Then
///
/// $f(x, k, r) = (g(x, k, r), \operatorname{cmp}(g(x, k, r), q))$.
///
/// # Worst-case complexity
/// $T(n, m) = O(n + m)$
///
/// $M(n, m) = O(n + m)$
///
/// where $T$ is time, $M$ is additional memory, $n$ is `self.significant_bits()`, and
/// $m$ is `max(bits, 0)`.
///
/// # Panics
/// Let $k$ be `bits`. Panics if $k$ is negative and `rm` is `Exact` but `self` is not
/// divisible by $2^{-k}$.
///
/// # Examples
/// See [here](super::shl_round#shl_round).
#[inline]
fn shl_round(self, bits: $t, rm: RoundingMode) -> (Natural, Ordering) {
shl_round_ref(self, bits, rm)
}
}
impl ShlRoundAssign<$t> for Natural {
/// Left-shifts a [`Natural`] (multiplies or divides it by a power of 2) and rounds
/// according to the specified rounding mode, in place. An [`Ordering`] is returned,
/// indicating whether the assigned value is less than, equal to, or greater than the
/// exact value.
///
/// Passing `Floor` or `Down` is equivalent to using `>>`. To test whether `Exact` can
/// be passed, use `bits > 0 || self.divisible_by_power_of_2(bits)`. Rounding might only
/// be necessary if `bits` is negative.
///
/// See the [`ShlRound`] documentation for details.
///
/// # Worst-case complexity
/// $T(n, m) = O(n + m)$
///
/// $M(n, m) = O(n + m)$
///
/// where $T$ is time, $M$ is additional memory, $n$ is `self.significant_bits()`, and
/// $m$ is `max(bits, 0)`.
///
/// # Panics
/// Let $k$ be `bits`. Panics if $k$ is negative and `rm` is `Exact` but `self` is not
/// divisible by $2^{-k}$.
///
/// # Examples
/// See [here](super::shl_round#shl_round_assign).
#[inline]
fn shl_round_assign(&mut self, bits: $t, rm: RoundingMode) -> Ordering {
shl_round_assign_n(self, bits, rm)
}
}
};
}
apply_to_signeds!(impl_natural_shl_round_signed);