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use crate::num::arithmetic::traits::{NextPowerOf2, NextPowerOf2Assign, PowerOf2, Sign};
use crate::num::basic::floats::PrimitiveFloat;
use crate::num::conversion::traits::SciMantissaAndExponent;
use std::cmp::Ordering;
macro_rules! impl_next_power_of_2_unsigned {
($t:ident) => {
impl NextPowerOf2 for $t {
type Output = $t;
/// This is a wrapper over the `next_power_of_two` functions in the standard library,
/// for example [this one](u32::next_power_of_two).
#[inline]
fn next_power_of_2(self) -> $t {
$t::next_power_of_two(self)
}
}
impl NextPowerOf2Assign for $t {
/// Replaces a number with the smallest power of 2 greater than or equal to it.
///
/// $x \gets 2^{\lceil \log_2 x \rceil}$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if the next power of 2 is greater than the type's maximum value.
///
/// # Examples
/// See [here](super::next_power_of_2#next_power_of_2_assign).
#[inline]
fn next_power_of_2_assign(&mut self) {
*self = $t::next_power_of_2(*self);
}
}
};
}
apply_to_unsigneds!(impl_next_power_of_2_unsigned);
macro_rules! impl_next_power_of_2_primitive_float {
($t:ident) => {
impl NextPowerOf2 for $t {
type Output = $t;
/// Finds the smallest power of 2 greater than or equal to a number.
///
/// $x \gets 2^{\lceil \log_2 x \rceil}$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `self` has a negative sign (positive zero is allowed, but negative zero
/// is not), or if the next power of 2 is greater than the type's maximum value.
///
/// # Examples
/// See [here](super::next_power_of_2#next_power_of_2).
#[inline]
fn next_power_of_2(self) -> $t {
assert_eq!(self.sign(), Ordering::Greater);
assert!(self.is_finite());
if self == 0.0 {
return $t::MIN_POSITIVE_SUBNORMAL;
}
let (mantissa, exponent) = self.sci_mantissa_and_exponent();
if mantissa == 1.0 {
self
} else if exponent == $t::MAX_EXPONENT {
panic!("Next power of 2 is too large to represent");
} else {
$t::power_of_2(exponent + 1)
}
}
}
impl NextPowerOf2Assign for $t {
/// Replaces a number with the smallest power of 2 greater than or equal to it.
///
/// $x \gets 2^{\lceil \log_2 x \rceil}$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if the next power of 2 is greater than the type's maximum value.
///
/// # Examples
/// See [here](super::next_power_of_2#next_power_of_2_assign).
#[inline]
fn next_power_of_2_assign(&mut self) {
*self = $t::next_power_of_2(*self);
}
}
};
}
apply_to_primitive_floats!(impl_next_power_of_2_primitive_float);