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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::num::arithmetic::traits::{ArithmeticCheckedShl, ArithmeticCheckedShr, UnsignedAbs};
use crate::num::basic::signeds::PrimitiveSigned;
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use core::ops::Shr;
fn arithmetic_checked_shr_unsigned_signed<
T: ArithmeticCheckedShl<U, Output = T> + PrimitiveUnsigned + Shr<U, Output = T>,
U: PrimitiveUnsigned,
S: PrimitiveSigned + UnsignedAbs<Output = U>,
>(
x: T,
bits: S,
) -> Option<T> {
if bits < S::ZERO {
x.arithmetic_checked_shl(bits.unsigned_abs())
} else {
let abs_bits = bits.unsigned_abs();
Some(if abs_bits >= U::wrapping_from(T::WIDTH) {
T::ZERO
} else {
x >> abs_bits
})
}
}
macro_rules! impl_arithmetic_checked_shr_unsigned_signed {
($t:ident) => {
macro_rules! impl_arithmetic_checked_shr_unsigned_signed_inner {
($u:ident) => {
impl ArithmeticCheckedShr<$u> for $t {
type Output = $t;
/// Shifts a number right (divides it by a power of 2). If the result is too
/// large to be represented, `None` is returned.
///
/// Zero may be shifted by any amount, and any number may be shifted by any
/// non-negative amount; shifting by a large amount returns `Some(0)`.
///
/// $$
/// f(x, b) = \\begin{cases}
/// \operatorname{Some}(\lfloor x/2^b \rfloor) &
/// \text{if} \\quad b \geq 0, \\\\
/// \operatorname{Some}(2^{-b} x) &
/// \text{if} \\quad b < 0 \\ \mathrm{and} \\ 2^{-b} x < 2^W, \\\\
/// \operatorname{None} &
/// \text{if} \\quad b < 0 \\ \mathrm{and} \\ 2^{-b} x \geq 2^W, \\\\
/// \\end{cases}
/// $$
/// where $W$ is `Self::WIDTH`.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::arithmetic_checked_shr#arithmetic_checked_shr).
#[inline]
fn arithmetic_checked_shr(self, bits: $u) -> Option<$t> {
arithmetic_checked_shr_unsigned_signed(self, bits)
}
}
};
}
apply_to_signeds!(impl_arithmetic_checked_shr_unsigned_signed_inner);
};
}
apply_to_unsigneds!(impl_arithmetic_checked_shr_unsigned_signed);
fn arithmetic_checked_shr_signed_signed<
T: ArithmeticCheckedShl<U, Output = T> + PrimitiveSigned + Shr<U, Output = T>,
U: PrimitiveUnsigned,
S: PrimitiveSigned + UnsignedAbs<Output = U>,
>(
x: T,
bits: S,
) -> Option<T> {
if bits < S::ZERO {
x.arithmetic_checked_shl(bits.unsigned_abs())
} else {
let width = U::wrapping_from(T::WIDTH);
let abs_bits = bits.unsigned_abs();
Some(if width != U::ZERO && abs_bits >= width {
-T::from(x < T::ZERO)
} else {
x >> abs_bits
})
}
}
macro_rules! impl_arithmetic_checked_shr_signed_signed {
($t:ident) => {
macro_rules! impl_arithmetic_checked_shr_signed_signed_inner {
($u:ident) => {
impl ArithmeticCheckedShr<$u> for $t {
type Output = $t;
/// Shifts a number right (divides it by a power of 2). If the result is too
/// large to be represented, `None` is returned.
///
/// Zero may be shifted by any amount, and any number may be shifted by any
/// non-negative amount; shifting by a large amount returns `Some(0)` if `self`
/// is positive, and `Some(-1)` if `self` is negative.
///
/// $$
/// f(x, b) = \\begin{cases}
/// \operatorname{Some}(\lfloor x/2^b \rfloor) &
/// \text{if} \\quad b \geq 0, \\\\
/// \operatorname{Some}(2^{-b} x) &
/// \text{if} \\quad b < 0 \\ \mathrm{and}
/// \\ -2^{W-1} \leq 2^{-b} x < 2^{W-1}, \\\\
/// \operatorname{None} &
/// \text{if} \\quad b < 0 \\ \mathrm{and}
/// \\ (2^{-b} x < -2^{W-1} \\ \mathrm{or}
/// \\ 2^{-b} x \geq 2^{W-1}), \\\\
/// \\end{cases}
/// $$
/// where $W$ is `Self::WIDTH`.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::arithmetic_checked_shr#arithmetic_checked_shr).
#[inline]
fn arithmetic_checked_shr(self, bits: $u) -> Option<$t> {
arithmetic_checked_shr_signed_signed(self, bits)
}
}
};
}
apply_to_signeds!(impl_arithmetic_checked_shr_signed_signed_inner);
};
}
apply_to_signeds!(impl_arithmetic_checked_shr_signed_signed);