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use crate::Counter;
use num_traits::{One, Zero};
use std::hash::{BuildHasher, Hash};
use std::ops::{Sub, SubAssign};
impl<I, T, N, S> Sub<I> for Counter<T, N, S>
where
I: IntoIterator<Item = T>,
T: Hash + Eq,
N: PartialOrd + SubAssign + Zero + One,
S: BuildHasher,
{
type Output = Self;
/// Consume `self` producing a `Counter` like `self` with the counts of the
/// elements of `I` subtracted, keeping only positive values.
///
/// ```rust
/// # use counter::Counter;
/// # use std::collections::HashMap;
/// let c = "aaab".chars().collect::<Counter<_>>();
/// let e = c - "abb".chars();
///
/// let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
/// assert_eq!(e.into_map(), expect);
/// ```
fn sub(mut self, rhs: I) -> Self::Output {
self.subtract(rhs);
self
}
}
impl<I, T, N> SubAssign<I> for Counter<T, N>
where
I: IntoIterator<Item = T>,
T: Hash + Eq,
N: PartialOrd + SubAssign + Zero + One,
{
/// Directly subtract the counts of the elements of `I` from `self`,
/// keeping only items with a value greater than [`N::zero()`].
///
/// [`N::zero()`]:
/// https://docs.rs/num-traits/latest/num_traits/identities/trait.Zero.html#tymethod.zero
///
/// ```rust
/// # use counter::Counter;
/// # use std::collections::HashMap;
/// let mut c = "aaab".chars().collect::<Counter<_>>();
/// c -= "abb".chars();
///
/// let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
/// assert_eq!(c.into_map(), expect);
/// ```
fn sub_assign(&mut self, rhs: I) {
self.subtract(rhs);
}
}