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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 malachite_base::num::arithmetic::traits::ShlRound;
use malachite_base::num::basic::traits::Zero;
use malachite_base::num::conversion::from::UnsignedFromFloatError;
use malachite_base::num::conversion::traits::{
ConvertibleFrom, IntegerMantissaAndExponent, IsInteger, RoundingFrom,
};
use malachite_base::rounding_modes::RoundingMode::{self, *};
macro_rules! float_impls {
($f: ident) => {
impl RoundingFrom<$f> for Natural {
/// Converts a floating-point value to a [`Natural`], using the specified rounding mode.
/// An [`Ordering`] is also returned, indicating whether the returned value is less
/// than, equal to, or greater than the original value.
///
/// The floating-point value cannot be NaN or infinite, and it cannot round to a
/// negative integer.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `value.sci_exponent()`.
///
/// # Panics
/// Panics if `value` is NaN or infinite, if it would round to a negative integer, or if
/// the rounding mode is `Exact` and `value` is not an integer.
///
/// # Examples
/// See [here](super::from_primitive_float#rounding_from).
fn rounding_from(value: $f, rm: RoundingMode) -> (Self, Ordering) {
if value.is_nan() || value == $f::INFINITY {
panic!("Cannot convert {} to Natural", value);
} else if value == 0.0 {
(Natural::ZERO, Equal)
} else if value < 0.0 {
if rm == Down || rm == Ceiling || rm == Nearest {
(Natural::ZERO, Greater)
} else {
panic!("Result is negative and cannot be converted to a Natural");
}
} else {
let (mantissa, exponent) = value.integer_mantissa_and_exponent();
Natural::from(mantissa).shl_round(exponent, rm)
}
}
}
impl TryFrom<$f> for Natural {
type Error = UnsignedFromFloatError;
/// Converts a floating-point value to a [`Natural`].
///
/// If the input isn't exactly equal to some [`Natural`], an error is returned.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `value.sci_exponent()`.
///
/// # Examples
/// See [here](super::from_primitive_float#try_from).
fn try_from(value: $f) -> Result<Natural, Self::Error> {
if value.is_nan() || value.is_infinite() {
Err(UnsignedFromFloatError::FloatInfiniteOrNan)
} else if value < 0.0 {
Err(UnsignedFromFloatError::FloatNegative)
} else if value == 0.0 {
Ok(Natural::ZERO)
} else {
let (mantissa, exponent) = value.integer_mantissa_and_exponent();
if exponent >= 0 {
Ok(Natural::from(mantissa) << exponent)
} else {
Err(UnsignedFromFloatError::FloatNonIntegerOrOutOfRange)
}
}
}
}
impl ConvertibleFrom<$f> for Natural {
/// Determines whether a floating-point value can be exactly converted to a [`Natural`].
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::from_primitive_float#convertible_from).
#[inline]
fn convertible_from(value: $f) -> bool {
value >= 0.0 && value.is_integer()
}
}
};
}
apply_to_primitive_floats!(float_impls);