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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::cmp::Ordering;
use malachite_base::num::arithmetic::traits::DivRound;
use malachite_base::num::conversion::traits::{ConvertibleFrom, RoundingFrom};
use malachite_base::rounding_modes::RoundingMode;
use malachite_nz::integer::Integer;
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct IntegerFromRationalError;
impl TryFrom<Rational> for Integer {
type Error = IntegerFromRationalError;
/// Converts a [`Rational`] to an [`Integer`], taking the [`Rational`] by value. If the
/// [`Rational`] is not an integer, an error is returned.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_nz::integer::Integer;
/// use malachite_q::conversion::integer_from_rational::IntegerFromRationalError;
/// use malachite_q::Rational;
///
/// assert_eq!(Integer::try_from(Rational::from(123)).unwrap(), 123);
/// assert_eq!(Integer::try_from(Rational::from(-123)).unwrap(), -123);
/// assert_eq!(
/// Integer::try_from(Rational::from_signeds(22, 7)),
/// Err(IntegerFromRationalError)
/// );
/// ```
fn try_from(x: Rational) -> Result<Self, Self::Error> {
if x.denominator == 1u32 {
Ok(Self::from_sign_and_abs(x.sign, x.numerator))
} else {
Err(IntegerFromRationalError)
}
}
}
impl TryFrom<&Rational> for Integer {
type Error = IntegerFromRationalError;
/// Converts a [`Rational`] to an [`Integer`], taking the [`Rational`] by reference. If the
/// [`Rational`] is not an integer, 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 `x.significant_bits()`.
///
/// # Examples
/// ```
/// use malachite_nz::integer::Integer;
/// use malachite_q::conversion::integer_from_rational::IntegerFromRationalError;
/// use malachite_q::Rational;
///
/// assert_eq!(Integer::try_from(&Rational::from(123)).unwrap(), 123);
/// assert_eq!(Integer::try_from(&Rational::from(-123)).unwrap(), -123);
/// assert_eq!(
/// Integer::try_from(&Rational::from_signeds(22, 7)),
/// Err(IntegerFromRationalError)
/// );
/// ```
fn try_from(x: &Rational) -> Result<Self, Self::Error> {
if x.denominator == 1u32 {
Ok(Self::from_sign_and_abs_ref(x.sign, &x.numerator))
} else {
Err(IntegerFromRationalError)
}
}
}
impl ConvertibleFrom<&Rational> for Integer {
/// Determines whether a [`Rational`] can be converted to an [`Integer`], taking the
/// [`Rational`] by reference.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_base::num::conversion::traits::ConvertibleFrom;
/// use malachite_nz::integer::Integer;
/// use malachite_q::Rational;
///
/// assert_eq!(Integer::convertible_from(&Rational::from(123)), true);
/// assert_eq!(Integer::convertible_from(&Rational::from(-123)), true);
/// assert_eq!(
/// Integer::convertible_from(&Rational::from_signeds(22, 7)),
/// false
/// );
/// ```
#[inline]
fn convertible_from(x: &Rational) -> bool {
x.denominator == 1u32
}
}
impl RoundingFrom<Rational> for Integer {
/// Converts a [`Rational`] to an [`Integer`], using a specified [`RoundingMode`] and taking the
/// [`Rational`] by value. An [`Ordering`] is also returned, indicating whether the returned
/// value is less than, equal to, or greater than the original value.
///
/// # Worst-case complexity
/// $T(n) = O(n \log n \log\log n)$
///
/// $M(n) = O(n \log n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `x.significant_bits()`.
///
/// # Panics
/// Panics if the [`Rational`] is not an integer and `rm` is `Exact`.
///
/// # Examples
/// ```
/// use malachite_base::num::conversion::traits::RoundingFrom;
/// use malachite_base::rounding_modes::RoundingMode::*;
/// use malachite_base::strings::ToDebugString;
/// use malachite_nz::integer::Integer;
/// use malachite_q::Rational;
///
/// assert_eq!(
/// Integer::rounding_from(Rational::from(123), Exact).to_debug_string(),
/// "(123, Equal)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from(-123), Exact).to_debug_string(),
/// "(-123, Equal)"
/// );
///
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(22, 7), Floor).to_debug_string(),
/// "(3, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(22, 7), Down).to_debug_string(),
/// "(3, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(22, 7), Ceiling).to_debug_string(),
/// "(4, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(22, 7), Up).to_debug_string(),
/// "(4, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(22, 7), Nearest).to_debug_string(),
/// "(3, Less)"
/// );
///
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Floor).to_debug_string(),
/// "(-4, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Down).to_debug_string(),
/// "(-3, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Ceiling).to_debug_string(),
/// "(-3, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Up).to_debug_string(),
/// "(-4, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Nearest).to_debug_string(),
/// "(-3, Greater)"
/// );
/// ```
fn rounding_from(x: Rational, rm: RoundingMode) -> (Self, Ordering) {
let s = x.sign;
let (n, o) = x
.numerator
.div_round(x.denominator, if s { rm } else { -rm });
(
Self::from_sign_and_abs(x.sign, n),
if s { o } else { o.reverse() },
)
}
}
impl RoundingFrom<&Rational> for Integer {
/// Converts a [`Rational`] to an [`Integer`], using a specified [`RoundingMode`] and taking the
/// [`Rational`] by reference. An [`Ordering`] is also returned, indicating whether the returned
/// value is less than, equal to, or greater than the original value.
///
/// # Worst-case complexity
/// $T(n) = O(n \log n \log\log n)$
///
/// $M(n) = O(n \log n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `x.significant_bits()`.
///
/// # Panics
/// Panics if the [`Rational`] is not an integer and `rm` is `Exact`.
///
/// # Examples
/// ```
/// use malachite_base::num::conversion::traits::RoundingFrom;
/// use malachite_base::rounding_modes::RoundingMode::*;
/// use malachite_base::strings::ToDebugString;
/// use malachite_nz::integer::Integer;
/// use malachite_q::Rational;
///
/// assert_eq!(
/// Integer::rounding_from(&Rational::from(123), Exact).to_debug_string(),
/// "(123, Equal)"
/// );
/// assert_eq!(
/// Integer::rounding_from(&Rational::from(-123), Exact).to_debug_string(),
/// "(-123, Equal)"
/// );
///
/// assert_eq!(
/// Integer::rounding_from(&Rational::from_signeds(22, 7), Floor).to_debug_string(),
/// "(3, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(&Rational::from_signeds(22, 7), Down).to_debug_string(),
/// "(3, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(&Rational::from_signeds(22, 7), Ceiling).to_debug_string(),
/// "(4, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(&Rational::from_signeds(22, 7), Up).to_debug_string(),
/// "(4, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(&Rational::from_signeds(22, 7), Nearest).to_debug_string(),
/// "(3, Less)"
/// );
///
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Floor).to_debug_string(),
/// "(-4, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Down).to_debug_string(),
/// "(-3, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Ceiling).to_debug_string(),
/// "(-3, Greater)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Up).to_debug_string(),
/// "(-4, Less)"
/// );
/// assert_eq!(
/// Integer::rounding_from(Rational::from_signeds(-22, 7), Nearest).to_debug_string(),
/// "(-3, Greater)"
/// );
/// ```
fn rounding_from(x: &Rational, rm: RoundingMode) -> (Self, Ordering) {
let (n, o) = (&x.numerator).div_round(&x.denominator, if x.sign { rm } else { -rm });
(
Self::from_sign_and_abs(x.sign, n),
if x.sign { o } else { o.reverse() },
)
}
}