Struct linked_hash_set::LinkedHashSet

pub struct LinkedHashSet<T, S = RandomState> { /* fields omitted */ }

A linked hash set implemented as a linked_hash_map::LinkedHashMap where the value is (), in a similar way std HashSet is implemented from HashMap.

General usage is very similar to a std HashSet. However, a LinkedHashSet maintains insertion order using a doubly-linked list running through its entries. As such methods front(), pop_front(), back() and pop_back() are provided.

Examples

use linked_hash_set::LinkedHashSet;
// Type inference lets us omit an explicit type signature (which
// would be `LinkedHashSet<&str>` in this example).
let mut books = LinkedHashSet::new();

// Add some books.
books.insert("A Dance With Dragons");
books.insert("To Kill a Mockingbird");
books.insert("The Odyssey");
books.insert("The Great Gatsby");

// Check for a specific one.
if !books.contains("The Winds of Winter") {
    println!(
        "We have {} books, but The Winds of Winter ain't one.",
        books.len()
    );
}

// Remove a book.
books.remove("The Odyssey");

// Remove the first inserted book.
books.pop_front();

// Iterate over the remaining books in insertion order.
for book in &books {
    println!("{}", book);
}

assert_eq!(
    books.into_iter().collect::<Vec<_>>(),
    vec!["To Kill a Mockingbird", "The Great Gatsby"]
);

The easiest way to use LinkedHashSet with a custom type is to derive Eq and Hash. We must also derive PartialEq, this will in the future be implied by Eq.

use linked_hash_set::LinkedHashSet;
#[derive(Hash, Eq, PartialEq, Debug)]
struct Viking<'a> {
    name: &'a str,
    power: usize,
}

let mut vikings = LinkedHashSet::new();

vikings.insert(Viking { name: "Einar", power: 9 });
vikings.insert(Viking { name: "Einar", power: 9 });
vikings.insert(Viking { name: "Olaf", power: 4 });
vikings.insert(Viking { name: "Harald", power: 8 });

// Use derived implementation to print the vikings.
for x in &vikings {
    println!("{:?}", x);
}

A LinkedHashSet with fixed list of elements can be initialized from an array:

use linked_hash_set::LinkedHashSet;

fn main() {
    let viking_names: LinkedHashSet<&str> =
        [ "Einar", "Olaf", "Harald" ].iter().cloned().collect();
    // use the values stored in the set
}

Methods

impl<T: Hash + Eq> LinkedHashSet<T, RandomState>

pub fn new() -> LinkedHashSet<T, RandomState>

Creates an empty LinkedHashSet.

Examples

use linked_hash_set::LinkedHashSet;
let set: LinkedHashSet<i32> = LinkedHashSet::new();

pub fn with_capacity(capacity: usize) -> LinkedHashSet<T, RandomState>

Creates an empty LinkedHashSet with the specified capacity.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

Examples

use linked_hash_set::LinkedHashSet;
let set: LinkedHashSet<i32> = LinkedHashSet::with_capacity(10);
assert!(set.capacity() >= 10);

impl<T, S> LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

pub fn with_hasher(hasher: S) -> LinkedHashSet<T, S>

Creates a new empty hash set which will use the given hasher to hash keys.

The hash set is also created with the default initial capacity.

Warning: hasher is normally randomly generated, and is designed to allow LinkedHashSets to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

Examples

use linked_hash_set::LinkedHashSet;
use std::collections::hash_map::RandomState;

let s = RandomState::new();
let mut set = LinkedHashSet::with_hasher(s);
set.insert(2);

pub fn with_capacity_and_hasher(     capacity: usize,     hasher: S ) -> LinkedHashSet<T, S>

Creates an empty LinkedHashSet with with the specified capacity, using hasher to hash the keys.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

Warning: hasher is normally randomly generated, and is designed to allow LinkedHashSets to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

Examples

use linked_hash_set::LinkedHashSet;
use std::collections::hash_map::RandomState;

let s = RandomState::new();
let mut set = LinkedHashSet::with_capacity_and_hasher(10, s);
set.insert(1);

pub fn hasher(&self) -> &S

Returns a reference to the set's BuildHasher.

Examples

use linked_hash_set::LinkedHashSet;
use std::collections::hash_map::RandomState;

let hasher = RandomState::new();
let set: LinkedHashSet<i32> = LinkedHashSet::with_hasher(hasher);
let hasher: &RandomState = set.hasher();

pub fn capacity(&self) -> usize

Returns the number of elements the set can hold without reallocating.

Examples

use linked_hash_set::LinkedHashSet;
let set: LinkedHashSet<i32> = LinkedHashSet::with_capacity(100);
assert!(set.capacity() >= 100);

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more elements to be inserted in the LinkedHashSet. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new allocation size overflows usize.

Examples

use linked_hash_set::LinkedHashSet;
let mut set: LinkedHashSet<i32> = LinkedHashSet::new();
set.reserve(10);
assert!(set.capacity() >= 10);

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the set as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use linked_hash_set::LinkedHashSet;

let mut set = LinkedHashSet::with_capacity(100);
set.insert(1);
set.insert(2);
assert!(set.capacity() >= 100);
set.shrink_to_fit();
assert!(set.capacity() >= 2);

Important traits for Iter<'a, K>

impl<'a, K> Iterator for Iter<'a, K> type Item = &'a K;

pub fn iter(&self) -> Iter<T>

An iterator visiting all elements in insertion order. The iterator element type is &'a T.

Examples

use linked_hash_set::LinkedHashSet;
let mut set = LinkedHashSet::new();
set.insert("a");
set.insert("b");

// Will print in an insertion order.
for x in set.iter() {
    println!("{}", x);
}

Important traits for Difference<'a, T, S>

impl<'a, T, S> Iterator for Difference<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher,  type Item = &'a T;

pub fn difference<'a>(     &'a self,     other: &'a LinkedHashSet<T, S> ) -> Difference<'a, T, S>

Visits the values representing the difference, i.e. the values that are in self but not in other.

Examples

use linked_hash_set::LinkedHashSet;
let a: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let b: LinkedHashSet<_> = [4, 2, 3, 4].iter().cloned().collect();

// Can be seen as `a - b`.
for x in a.difference(&b) {
    println!("{}", x); // Print 1
}

let diff: LinkedHashSet<_> = a.difference(&b).collect();
assert_eq!(diff, [1].iter().collect());

// Note that difference is not symmetric,
// and `b - a` means something else:
let diff: LinkedHashSet<_> = b.difference(&a).collect();
assert_eq!(diff, [4].iter().collect());

Important traits for SymmetricDifference<'a, T, S>

impl<'a, T, S> Iterator for SymmetricDifference<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher,  type Item = &'a T;

pub fn symmetric_difference<'a>(     &'a self,     other: &'a LinkedHashSet<T, S> ) -> SymmetricDifference<'a, T, S>

Visits the values representing the symmetric difference, i.e. the values that are in self or in other but not in both.

Examples

use linked_hash_set::LinkedHashSet;
let a: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let b: LinkedHashSet<_> = [4, 2, 3, 4].iter().cloned().collect();

// Print 1, 4 in insertion order.
for x in a.symmetric_difference(&b) {
    println!("{}", x);
}

let diff1: LinkedHashSet<_> = a.symmetric_difference(&b).collect();
let diff2: LinkedHashSet<_> = b.symmetric_difference(&a).collect();

assert_eq!(diff1, diff2);
assert_eq!(diff1, [1, 4].iter().collect());

Important traits for Intersection<'a, T, S>

impl<'a, T, S> Iterator for Intersection<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher,  type Item = &'a T;

pub fn intersection<'a>(     &'a self,     other: &'a LinkedHashSet<T, S> ) -> Intersection<'a, T, S>

Visits the values representing the intersection, i.e. the values that are both in self and other.

Examples

use linked_hash_set::LinkedHashSet;
let a: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let b: LinkedHashSet<_> = [4, 2, 3, 4].iter().cloned().collect();

// Print 2, 3 in insertion order.
for x in a.intersection(&b) {
    println!("{}", x);
}

let intersection: LinkedHashSet<_> = a.intersection(&b).collect();
assert_eq!(intersection, [2, 3].iter().collect());

Important traits for Union<'a, T, S>

impl<'a, T, S> Iterator for Union<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher,  type Item = &'a T;

pub fn union<'a>(&'a self, other: &'a LinkedHashSet<T, S>) -> Union<'a, T, S>

Visits the values representing the union, i.e. all the values in self or other, without duplicates.

Examples

use linked_hash_set::LinkedHashSet;
let a: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let b: LinkedHashSet<_> = [4, 2, 3, 4].iter().cloned().collect();

// Print 1, 2, 3, 4 in insertion order.
for x in a.union(&b) {
    println!("{}", x);
}

let union: LinkedHashSet<_> = a.union(&b).collect();
assert_eq!(union, [1, 2, 3, 4].iter().collect());

pub fn len(&self) -> usize

Returns the number of elements in the set.

Examples

use linked_hash_set::LinkedHashSet;

let mut v = LinkedHashSet::new();
assert_eq!(v.len(), 0);
v.insert(1);
assert_eq!(v.len(), 1);

pub fn is_empty(&self) -> bool

Returns true if the set contains no elements.

Examples

use linked_hash_set::LinkedHashSet;

let mut v = LinkedHashSet::new();
assert!(v.is_empty());
v.insert(1);
assert!(!v.is_empty());

pub fn clear(&mut self)

Clears the set, removing all values.

Examples

use linked_hash_set::LinkedHashSet;

let mut v = LinkedHashSet::new();
v.insert(1);
v.clear();
assert!(v.is_empty());

pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool where     T: Borrow<Q>,     Q: Hash + Eq,

Returns true if the set contains a value.

The value may be any borrowed form of the set's value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use linked_hash_set::LinkedHashSet;

let set: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.contains(&1), true);
assert_eq!(set.contains(&4), false);

pub fn refresh<Q: ?Sized>(&mut self, value: &Q) -> bool where     T: Borrow<Q>,     Q: Hash + Eq,

If already present, moves a value to the end of the ordering.

If the set did have this value present, true is returned.

If the set did not have this value present, false is returned.

Similar to LinkedHashMap::get_refresh.

Examples

use linked_hash_set::LinkedHashSet;

let mut set: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let was_refreshed = set.refresh(&2);

assert_eq!(was_refreshed, true);
assert_eq!(set.into_iter().collect::<Vec<_>>(), vec![1, 3, 2]);

pub fn is_disjoint(&self, other: &LinkedHashSet<T, S>) -> bool

Returns true if self has no elements in common with other. This is equivalent to checking for an empty intersection.

Examples

use linked_hash_set::LinkedHashSet;

let a: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let mut b = LinkedHashSet::new();

assert_eq!(a.is_disjoint(&b), true);
b.insert(4);
assert_eq!(a.is_disjoint(&b), true);
b.insert(1);
assert_eq!(a.is_disjoint(&b), false);

pub fn is_subset(&self, other: &LinkedHashSet<T, S>) -> bool

Returns true if the set is a subset of another, i.e. other contains at least all the values in self.

Examples

use linked_hash_set::LinkedHashSet;

let sup: LinkedHashSet<_> = [1, 2, 3].iter().cloned().collect();
let mut set = LinkedHashSet::new();

assert_eq!(set.is_subset(&sup), true);
set.insert(2);
assert_eq!(set.is_subset(&sup), true);
set.insert(4);
assert_eq!(set.is_subset(&sup), false);

pub fn is_superset(&self, other: &LinkedHashSet<T, S>) -> bool

Returns true if the set is a superset of another, i.e. self contains at least all the values in other.

Examples

use linked_hash_set::LinkedHashSet;

let sub: LinkedHashSet<_> = [1, 2].iter().cloned().collect();
let mut set = LinkedHashSet::new();

assert_eq!(set.is_superset(&sub), false);

set.insert(0);
set.insert(1);
assert_eq!(set.is_superset(&sub), false);

set.insert(2);
assert_eq!(set.is_superset(&sub), true);

pub fn insert(&mut self, value: T) -> bool

Adds a value to the set.

If the set did not have this value present, true is returned.

If the set did have this value present, false is returned.

Note that performing this action will always place the value at the end of the ordering whether the set already contained the value or not. Also see insert_if_absent.

Examples

use linked_hash_set::LinkedHashSet;

let mut set = LinkedHashSet::new();

assert_eq!(set.insert(2), true);
assert_eq!(set.insert(2), false);
assert_eq!(set.len(), 1);

pub fn insert_if_absent(&mut self, value: T) -> bool

Adds a value to the set, if not already present. The distinction with insert is that order of elements is unaffected when calling this method for a value already contained.

If the set did not have this value present, true is returned.

If the set did have this value present, false is returned.

Examples

use linked_hash_set::LinkedHashSet;

let mut set = LinkedHashSet::new();

assert_eq!(set.insert_if_absent(2), true);
assert_eq!(set.insert_if_absent(2), false);
assert_eq!(set.len(), 1);

pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool where     T: Borrow<Q>,     Q: Hash + Eq,

Removes a value from the set. Returns true if the value was present in the set.

The value may be any borrowed form of the set's value type, but Hash and Eq on the borrowed form must match those for the value type.

This operation will not affect the ordering of the other elements.

Examples

use linked_hash_set::LinkedHashSet;

let mut set = LinkedHashSet::new();

set.insert(2);
assert_eq!(set.remove(&2), true);
assert_eq!(set.remove(&2), false);

pub fn front(&self) -> Option<&T>

Gets the first entry.

pub fn pop_front(&mut self) -> Option<T>

Removes the first entry.

pub fn back(&mut self) -> Option<&T>

Gets the last entry.

pub fn pop_back(&mut self) -> Option<T>

Removes the last entry.

Trait Implementations

impl<T: Hash + Eq + Clone, S: BuildHasher + Clone> Clone for LinkedHashSet<T, S>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, S> PartialEq for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

fn eq(&self, other: &LinkedHashSet<T, S>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T, S> Hash for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where     H: Hasher,

Feeds a slice of this type into the given [Hasher].

impl<T, S> Eq for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

impl<T, S> Debug for LinkedHashSet<T, S> where     T: Eq + Hash + Debug,     S: BuildHasher,

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T, S> FromIterator<T> for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher + Default,

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> LinkedHashSet<T, S>

Creates a value from an iterator.

impl<T, S> Extend<T> for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

impl<'a, T, S> Extend<&'a T> for LinkedHashSet<T, S> where     T: 'a + Eq + Hash + Copy,     S: BuildHasher,

fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

impl<T, S> Default for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher + Default,

fn default() -> LinkedHashSet<T, S>

Creates an empty LinkedHashSet<T, S> with the Default value for the hasher.

impl<'a, 'b, T, S> BitOr<&'b LinkedHashSet<T, S>> for &'a LinkedHashSet<T, S> where     T: Eq + Hash + Clone,     S: BuildHasher + Default,

type Output = LinkedHashSet<T, S>

The resulting type after applying the | operator.

fn bitor(self, rhs: &LinkedHashSet<T, S>) -> LinkedHashSet<T, S>

Returns the union of self and rhs as a new LinkedHashSet<T, S>.

Examples

use linked_hash_set::LinkedHashSet;

let a: LinkedHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LinkedHashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a | &b;

let mut i = 0;
let expected = [1, 2, 3, 4, 5];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<'a, 'b, T, S> BitAnd<&'b LinkedHashSet<T, S>> for &'a LinkedHashSet<T, S> where     T: Eq + Hash + Clone,     S: BuildHasher + Default,

type Output = LinkedHashSet<T, S>

The resulting type after applying the & operator.

fn bitand(self, rhs: &LinkedHashSet<T, S>) -> LinkedHashSet<T, S>

Returns the intersection of self and rhs as a new LinkedHashSet<T, S>.

Examples

use linked_hash_set::LinkedHashSet;

let a: LinkedHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LinkedHashSet<_> = vec![2, 3, 4].into_iter().collect();

let set = &a & &b;

let mut i = 0;
let expected = [2, 3];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<'a, 'b, T, S> BitXor<&'b LinkedHashSet<T, S>> for &'a LinkedHashSet<T, S> where     T: Eq + Hash + Clone,     S: BuildHasher + Default,

type Output = LinkedHashSet<T, S>

The resulting type after applying the ^ operator.

fn bitxor(self, rhs: &LinkedHashSet<T, S>) -> LinkedHashSet<T, S>

Returns the symmetric difference of self and rhs as a new LinkedHashSet<T, S>.

Examples

use linked_hash_set::LinkedHashSet;

let a: LinkedHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LinkedHashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a ^ &b;

let mut i = 0;
let expected = [1, 2, 4, 5];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<'a, 'b, T, S> Sub<&'b LinkedHashSet<T, S>> for &'a LinkedHashSet<T, S> where     T: Eq + Hash + Clone,     S: BuildHasher + Default,

type Output = LinkedHashSet<T, S>

The resulting type after applying the - operator.

fn sub(self, rhs: &LinkedHashSet<T, S>) -> LinkedHashSet<T, S>

Returns the difference of self and rhs as a new LinkedHashSet<T, S>.

Examples

use linked_hash_set::LinkedHashSet;

let a: LinkedHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LinkedHashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a - &b;

let mut i = 0;
let expected = [1, 2];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<'a, T, S> IntoIterator for &'a LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

Important traits for Iter<'a, K>

impl<'a, K> Iterator for Iter<'a, K> type Item = &'a K;

fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value.

impl<T, S> IntoIterator for LinkedHashSet<T, S> where     T: Eq + Hash,     S: BuildHasher,

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

Important traits for IntoIter<K>

impl<K> Iterator for IntoIter<K> type Item = K;

fn into_iter(self) -> IntoIter<T>

Creates a consuming iterator, that is, one that moves each value out of the set in insertion order. The set cannot be used after calling this.

Examples

use linked_hash_set::LinkedHashSet;
let mut set = LinkedHashSet::new();
set.insert("a".to_string());
set.insert("b".to_string());

// Not possible to collect to a Vec<String> with a regular `.iter()`.
let v: Vec<String> = set.into_iter().collect();

// Will print in an insertion order.
for x in &v {
    println!("{}", x);
}