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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_polynomial::RationalPolynomial;
use malachite_base::polynomial::{DeflatePowerOfX, DeflatePowerOfXAssign};
impl DeflatePowerOfX for RationalPolynomial {
type Output = Self;
/// Deflates a [`RationalPolynomial`] by $n$, taking it by value, giving the polynomial $q$ with
/// $q(x^n) = p(x)$. The coefficient of $x^{in}$ moves to $x^i$.
///
/// $$
/// f(p, n) = q, \quad \text{where} \quad q(x^n) = p(x).
/// $$
///
/// Only the numerator changes, so the result stays in lowest terms. A constant polynomial
/// deflates to itself, and deflating by 1 changes nothing.
///
/// # Worst-case complexity
/// $T(m) = O(m)$
///
/// $M(m) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $m$ is `self.len()`.
///
/// # Panics
/// Panics if `n` is 0, or if the polynomial has a nonzero coefficient at an exponent that is
/// not a multiple of `n`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::polynomial::DeflatePowerOfX;
/// use malachite_q::rational_polynomial::RationalPolynomial;
///
/// let p = RationalPolynomial::from_str("1/2*x^4-1/3").unwrap();
/// assert_eq!(p.deflate_power_of_x(2).to_string(), "1/2*x^2-1/3");
/// ```
///
/// FLINT has no `fmpq_poly_deflate`; this corresponds to `fmpz_poly_deflate` from
/// `fmpz_poly/deflate.c`, FLINT 3.6.0, applied to the numerator, except that it panics rather
/// than dropping the coefficients at other exponents.
#[inline]
fn deflate_power_of_x(mut self, n: u64) -> Self {
self.deflate_power_of_x_assign(n);
self
}
}
impl DeflatePowerOfX for &RationalPolynomial {
type Output = RationalPolynomial;
/// Deflates a [`RationalPolynomial`] by $n$, taking it by reference, giving the polynomial $q$
/// with $q(x^n) = p(x)$. The coefficient of $x^{in}$ moves to $x^i$.
///
/// $$
/// f(p, n) = q, \quad \text{where} \quad q(x^n) = p(x).
/// $$
///
/// Only the numerator changes, so the result stays in lowest terms. A constant polynomial
/// deflates to itself, and deflating by 1 changes nothing.
///
/// # Worst-case complexity
/// $T(m) = O(m)$
///
/// $M(m) = O(m)$
///
/// where $T$ is time, $M$ is additional memory, and $m$ is the total number of bits of the
/// numerator's coefficients and the denominator.
///
/// # Panics
/// Panics if `n` is 0, or if the polynomial has a nonzero coefficient at an exponent that is
/// not a multiple of `n`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::polynomial::DeflatePowerOfX;
/// use malachite_q::rational_polynomial::RationalPolynomial;
///
/// let p = RationalPolynomial::from_str("1/2*x^4-1/3").unwrap();
/// assert_eq!((&p).deflate_power_of_x(2).to_string(), "1/2*x^2-1/3");
/// ```
///
/// FLINT has no `fmpq_poly_deflate`; this corresponds to `fmpz_poly_deflate` from
/// `fmpz_poly/deflate.c`, FLINT 3.6.0, applied to the numerator, except that it panics rather
/// than dropping the coefficients at other exponents.
fn deflate_power_of_x(self, n: u64) -> RationalPolynomial {
RationalPolynomial {
numerator: (&self.numerator).deflate_power_of_x(n),
denominator: self.denominator.clone(),
}
}
}
impl DeflatePowerOfXAssign for RationalPolynomial {
/// Deflates a [`RationalPolynomial`] by $n$ in place, replacing $p$ with the polynomial $q$
/// such that $q(x^n) = p(x)$. The coefficient of $x^{in}$ moves to $x^i$.
///
/// $$
/// p \gets q, \quad \text{where} \quad q(x^n) = p(x).
/// $$
///
/// Only the numerator changes, so the result stays in lowest terms. A constant polynomial
/// deflates to itself, and deflating by 1 changes nothing.
///
/// # Worst-case complexity
/// $T(m) = O(m)$
///
/// $M(m) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $m$ is `self.len()`.
///
/// # Panics
/// Panics if `n` is 0, or if the polynomial has a nonzero coefficient at an exponent that is
/// not a multiple of `n`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::polynomial::DeflatePowerOfXAssign;
/// use malachite_q::rational_polynomial::RationalPolynomial;
///
/// let mut p = RationalPolynomial::from_str("1/2*x^4-1/3").unwrap();
/// p.deflate_power_of_x_assign(2);
/// assert_eq!(p.to_string(), "1/2*x^2-1/3");
/// ```
///
/// FLINT has no `fmpq_poly_deflate`; this corresponds to `fmpz_poly_deflate` from
/// `fmpz_poly/deflate.c`, FLINT 3.6.0, applied to the numerator, except that it panics rather
/// than dropping the coefficients at other exponents.
#[inline]
fn deflate_power_of_x_assign(&mut self, n: u64) {
self.numerator.deflate_power_of_x_assign(n);
}
}