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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::{Parity, UnsignedAbs, WrappingPow, WrappingPowAssign};
use crate::num::basic::signeds::PrimitiveSigned;
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use crate::num::conversion::traits::WrappingFrom;
use crate::num::logic::traits::BitIterable;
fn wrapping_pow_unsigned<T: PrimitiveUnsigned>(x: T, exp: u64) -> T {
if exp == 0 {
T::ONE
} else if x < T::TWO {
x
} else {
let mut power = x;
for bit in exp.bits().rev().skip(1) {
power.wrapping_square_assign();
if bit {
power.wrapping_mul_assign(x);
}
}
power
}
}
fn wrapping_pow_signed<
U: PrimitiveUnsigned,
S: PrimitiveSigned + UnsignedAbs<Output = U> + WrappingFrom<U>,
>(
x: S,
exp: u64,
) -> S {
let p_abs = x.unsigned_abs().wrapping_pow(exp);
if x >= S::ZERO || exp.even() {
S::wrapping_from(p_abs)
} else {
S::wrapping_from(p_abs).wrapping_neg()
}
}
macro_rules! impl_wrapping_pow_unsigned {
($t:ident) => {
impl WrappingPow<u64> for $t {
type Output = $t;
/// This is a wrapper over the `wrapping_pow` functions in the standard library, for
/// example [this one](u32::wrapping_pow).
#[inline]
fn wrapping_pow(self, exp: u64) -> $t {
wrapping_pow_unsigned(self, exp)
}
}
};
}
apply_to_unsigneds!(impl_wrapping_pow_unsigned);
macro_rules! impl_wrapping_pow_signed {
($t:ident) => {
impl WrappingPow<u64> for $t {
type Output = $t;
/// This is a wrapper over the `wrapping_pow` functions in the standard library, for
/// example [this one](i32::wrapping_pow).
#[inline]
fn wrapping_pow(self, exp: u64) -> $t {
wrapping_pow_signed(self, exp)
}
}
};
}
apply_to_signeds!(impl_wrapping_pow_signed);
macro_rules! impl_wrapping_pow_primitive_int {
($t:ident) => {
impl WrappingPowAssign<u64> for $t {
/// Raises a number to a power, in place, wrapping around at the boundary of the type.
///
/// $x \gets y$, where $y \equiv x^n \mod 2^W$ and $W$ is `Self::WIDTH`.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::wrapping_pow#wrapping_pow_assign).
#[inline]
fn wrapping_pow_assign(&mut self, exp: u64) {
*self = WrappingPow::wrapping_pow(*self, exp);
}
}
};
}
apply_to_primitive_ints!(impl_wrapping_pow_primitive_int);