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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::Rational;
use core::ops::{Shl, ShlAssign, Shr, ShrAssign};
use malachite_base::num::arithmetic::traits::UnsignedAbs;
use malachite_base::num::basic::traits::Zero;
use malachite_base::num::conversion::traits::ExactFrom;
fn shr_unsigned_assign<T>(x: &mut Rational, bits: T)
where
u64: TryFrom<T>,
{
if *x == 0u32 {
return;
}
let numerator_zeros = x.numerator.trailing_zeros().unwrap();
let bits_64 = u64::exact_from(bits);
if numerator_zeros >= bits_64 {
x.numerator >>= bits_64;
} else {
x.denominator <<= bits_64 - numerator_zeros;
x.numerator >>= numerator_zeros;
}
}
fn shr_unsigned_ref<T>(x: &Rational, bits: T) -> Rational
where
u64: TryFrom<T>,
{
if *x == 0u32 {
return x.clone();
}
let numerator_zeros = x.numerator.trailing_zeros().unwrap();
let bits_64 = u64::exact_from(bits);
if numerator_zeros >= bits_64 {
Rational {
sign: x.sign,
numerator: &x.numerator >> bits_64,
denominator: x.denominator.clone(),
}
} else {
Rational {
sign: x.sign,
numerator: &x.numerator >> numerator_zeros,
denominator: &x.denominator << (bits_64 - numerator_zeros),
}
}
}
macro_rules! impl_shr_unsigned {
($t:ident) => {
impl Shr<$t> for Rational {
type Output = Rational;
/// Right-shifts a [`Rational`] (divides it by a power of 2), taking it by value.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr).
#[inline]
fn shr(mut self, bits: $t) -> Rational {
self >>= bits;
self
}
}
impl Shr<$t> for &Rational {
type Output = Rational;
/// Right-shifts a [`Rational`] (divides it by a power of 2), taking it by reference.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr).
#[inline]
fn shr(self, bits: $t) -> Rational {
shr_unsigned_ref(self, bits)
}
}
impl ShrAssign<$t> for Rational {
/// Right-shifts a [`Rational`] (divides it by a power of 2), in place.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr_assign).
#[inline]
fn shr_assign(&mut self, bits: $t) {
shr_unsigned_assign(self, bits);
}
}
};
}
apply_to_unsigneds!(impl_shr_unsigned);
fn shr_signed_ref<'a, U, S: Copy + Ord + UnsignedAbs<Output = U> + Zero>(
x: &'a Rational,
bits: S,
) -> Rational
where
&'a Rational: Shl<U, Output = Rational> + Shr<U, Output = Rational>,
{
if bits >= S::ZERO {
x >> bits.unsigned_abs()
} else {
x << bits.unsigned_abs()
}
}
fn shr_assign_signed<U, S: Copy + Ord + UnsignedAbs<Output = U> + Zero>(x: &mut Rational, bits: S)
where
Rational: ShlAssign<U> + ShrAssign<U>,
{
if bits >= S::ZERO {
*x >>= bits.unsigned_abs();
} else {
*x <<= bits.unsigned_abs();
}
}
macro_rules! impl_shr_signed {
($t:ident) => {
impl Shr<$t> for Rational {
type Output = Rational;
/// Right-shifts a [`Rational`] (divides it by a power of 2), taking it by value.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr).
#[inline]
fn shr(mut self, bits: $t) -> Rational {
self >>= bits;
self
}
}
impl Shr<$t> for &Rational {
type Output = Rational;
/// Right-shifts a [`Rational`] (divides it by a power of 2), taking it by reference.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr).
#[inline]
fn shr(self, bits: $t) -> Rational {
shr_signed_ref(self, bits)
}
}
impl ShrAssign<$t> for Rational {
/// Right-shifts a [`Rational`] (divides it by a power of 2), in reference.
///
/// $$
/// f(x, k) = \frac{x}{2^k}.
/// $$
///
/// # 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)`.
///
/// See [here](super::shr#shr_assign).
#[inline]
fn shr_assign(&mut self, bits: $t) {
shr_assign_signed(self, bits)
}
}
};
}
apply_to_signeds!(impl_shr_signed);