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use crate::num::arithmetic::traits::{ModSub, ModSubAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
fn mod_sub<T: PrimitiveUnsigned>(x: T, other: T, m: T) -> T {
let diff = x.wrapping_sub(other);
if x < other {
m.wrapping_add(diff)
} else {
diff
}
}
macro_rules! impl_mod_sub {
($t:ident) => {
impl ModSub<$t> for $t {
type Output = $t;
/// Subtracts two numbers modulo a third number $m$. Assumes the inputs are already
/// reduced modulo $m$.
///
/// $f(x, y, m) = z$, where $x, y, z < m$ and $x - y \equiv z \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::mod_sub#mod_sub).
///
/// This is equivalent to `nmod_sub` from `nmod_vec.h`, FLINT 2.7.1.
#[inline]
fn mod_sub(self, other: $t, m: $t) -> $t {
mod_sub(self, other, m)
}
}
impl ModSubAssign<$t> for $t {
/// Subtracts two numbers modulo a third number $m$, in place. Assumes the inputs are
/// already reduced modulo $m$.
///
/// $x \gets z$, where $x, y, z < m$ and $x - y \equiv z \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::mod_sub#mod_sub_assign).
///
/// This is equivalent to `nmod_sub` from `nmod_vec.h`, FLINT 2.7.1, where the result
/// is assigned to `a`.
#[inline]
fn mod_sub_assign(&mut self, other: $t, m: $t) {
*self = self.mod_sub(other, m);
}
}
};
}
apply_to_unsigneds!(impl_mod_sub);