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Implement PartialOrd for HashSet #15647

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15 changes: 14 additions & 1 deletion src/libstd/collections/hashmap.rs
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,8 @@
//! Unordered containers, implemented as hash-tables (`HashSet` and `HashMap` types)

use clone::Clone;
use cmp::{max, Eq, Equiv, PartialEq};
use cmp;
use cmp::{max, Eq, Equiv, PartialEq, PartialOrd, Ordering};
use collections::{Collection, Mutable, Set, MutableSet, Map, MutableMap};
use default::Default;
use fmt::Show;
Expand Down Expand Up @@ -1499,6 +1500,18 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> PartialEq for HashSet<T, H> {

impl<T: Eq + Hash<S>, S, H: Hasher<S>> Eq for HashSet<T, H> {}

impl<T: Eq + Hash<S>, S, H: Hasher<S>> PartialOrd for HashSet<T, H> {
#[inline]
fn partial_cmp(&self, other: &HashSet<T, H>) -> Option<Ordering> {
match (self.is_subset(other), other.is_subset(self)) {
(true, true) => Some(cmp::Equal),
(true, false) => Some(cmp::Less),
(false, true) => Some(cmp::Greater),
(false, false) => None
}
}
}

impl<T: Eq + Hash<S>, S, H: Hasher<S>> Collection for HashSet<T, H> {
fn len(&self) -> uint { self.map.len() }
}
Expand Down