Struct nimiq_collections::limit_hash_set::LimitHashSet

pub struct LimitHashSet<T> where
    T: Hash + Eq,  { /* fields omitted */ }

A hash set implemented as UniqueLinkedList that has a limit on the number of elements.

As with the UniqueLinkedList type, a LimitHashSet requires that the elements implement the Eq and Hash traits. This can frequently be achieved by using #[derive(PartialEq, Eq, Hash)]. If you implement these yourself, it is important that the following property holds:

k1 == k2 -> hash(k1) == hash(k2)

In other words, if two keys are equal, their hashes must be equal.

It is a logic error for an item to be modified in such a way that the item's hash, as determined by the Hash trait, or its equality, as determined by the Eq trait, changes while it is in the set. This is normally only possible through Cell, RefCell, global state, I/O, or unsafe code.

Examples

use nimiq_collections::LimitHashSet;
// Type inference lets us omit an explicit type signature (which
// would be `LimitHashSet<String>` in this example).
let mut books = LimitHashSet::new(3);

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

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

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

// Iterate over everything.
for book in &books {
    println!("{}", book);
}

The easiest way to use LimitHashSet 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 nimiq_collections::LimitHashSet;
#[derive(Hash, Eq, PartialEq, Debug)]
struct Viking {
    name: String,
    power: usize,
}

let mut vikings = LimitHashSet::new(3);

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

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

Methods

impl<T> LimitHashSet<T> where
    T: Hash + Eq, 

pub fn new(limit: usize) -> Self

Creates an empty LimitHashSet with a limit of limit elements. limit must be greater than zero or this function will panic.

Examples

use nimiq_collections::LimitHashSet;
let set: LimitHashSet<i32> = LimitHashSet::new(10);

Important traits for Iter<'a, T>

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

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

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

Examples

use nimiq_collections::LimitHashSet;
let mut set = LimitHashSet::new(10);
set.insert("a");
set.insert("b");

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

pub fn len(&self) -> usize

Returns the number of elements in the set.

Examples

use nimiq_collections::LimitHashSet;

let mut v = LimitHashSet::new(10);
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 nimiq_collections::LimitHashSet;

let mut v = LimitHashSet::new(10);
assert!(v.is_empty());
v.insert(1);
assert!(!v.is_empty());

pub fn clear(&mut self)

Clears the set, removing all values.

Examples

use nimiq_collections::LimitHashSet;

let mut v = LimitHashSet::new(10);
v.insert(1);
v.clear();
assert!(v.is_empty());

Important traits for Difference<'a, T>

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

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

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

Examples

use nimiq_collections::LimitHashSet;
let a: LimitHashSet<_> = [1, 2, 3].iter().cloned().collect();
let b: LimitHashSet<_> = [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: LimitHashSet<_> = a.difference(&b).collect();
assert_eq!(diff, [1].iter().collect());

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

Important traits for SymmetricDifference<'a, T>

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

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

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

Examples

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

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

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

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

Important traits for Intersection<'a, T>

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

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

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

Examples

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

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

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

Important traits for Union<'a, T>

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

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

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

Examples

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

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

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

pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool where
    Rc<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 nimiq_collections::LimitHashSet;

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

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

Returns a reference to the value in the set, if any, that is equal to the given 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 nimiq_collections::LimitHashSet;

let set: LimitHashSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.get(&2), Some(&2));
assert_eq!(set.get(&4), None);

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

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

Examples

use nimiq_collections::LimitHashSet;

let a: LimitHashSet<_> = [1, 2, 3].iter().cloned().collect();
let mut b = LimitHashSet::new(10);

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: &LimitHashSet<T>) -> bool

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

Examples

use nimiq_collections::LimitHashSet;

let sup: LimitHashSet<_> = [1, 2, 3].iter().cloned().collect();
let mut set = LimitHashSet::new(10);

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: &LimitHashSet<T>) -> bool

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

Examples

use nimiq_collections::LimitHashSet;

let sub: LimitHashSet<_> = [1, 2].iter().cloned().collect();
let mut set = LimitHashSet::new(10);

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 and removes the oldest value if the limit is reached.

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 nimiq_collections::LimitHashSet;

let mut set = LimitHashSet::new(10);

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

pub fn replace(&mut self, value: T) -> Option<T>

Adds a value to the set, replacing the existing value, if any, that is equal to the given one. Returns the replaced value. Removes the oldest value if the limit is reached.

Examples

use nimiq_collections::LimitHashSet;

let mut set = LimitHashSet::new(10);
set.insert(Vec::<i32>::new());

assert_eq!(set.get(&Vec::<i32>::new()).unwrap().capacity(), 0);
set.replace(Vec::with_capacity(10));
assert_eq!(set.get(&Vec::<i32>::new()).unwrap().capacity(), 10);

pub fn insert_and_get_removed(&mut self, value: T) -> Option<T>

Adds a value to the set, replacing the existing value, if any, that is equal to the given one. Removes and returns the oldest value if the limit is reached.

Examples

use nimiq_collections::LimitHashSet;

let mut set = LimitHashSet::new(2);
assert_eq!(set.insert_and_get_removed(4), None);
assert_eq!(set.insert_and_get_removed(3), None);
assert_eq!(set.insert_and_get_removed(5), Some(4));

pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool where
    Rc<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.

Examples

use nimiq_collections::LimitHashSet;

let mut set = LimitHashSet::new(10);

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

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

Removes and returns the value in the set, if any, that is equal to the given one.

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 nimiq_collections::LimitHashSet;

let mut set: LimitHashSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.take(&2), Some(2));
assert_eq!(set.take(&2), None);

Trait Implementations

impl<T> Extend<T> for LimitHashSet<T> where
    T: Eq + Hash, 

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

Extends a collection with the contents of an iterator.

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

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

Extends a collection with the contents of an iterator.

impl<'a, T> IntoIterator for &'a LimitHashSet<T> where
    T: Eq + Hash, 

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, T>

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

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

Creates an iterator from a value.

impl<T> IntoIterator for LimitHashSet<T> where
    T: Eq + Hash, 

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<T>

impl<T> Iterator for IntoIter<T> where
    T: Hash + Eq,  type Item = T;

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 nimiq_collections::LimitHashSet;
let mut set = LimitHashSet::new(10);
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 arbitrary order.
for x in &v {
    println!("{}", x);
}

impl<T: Clone> Clone for LimitHashSet<T> where
    T: Hash + Eq, 

fn clone(&self) -> LimitHashSet<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T> Eq for LimitHashSet<T> where
    T: Eq + Hash, 

impl<T> PartialEq<LimitHashSet<T>> for LimitHashSet<T> where
    T: Eq + Hash, 

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T> Debug for LimitHashSet<T> where
    T: Eq + Hash + Debug, 

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

Formats the value using the given formatter.

impl<'a, 'b, T> Sub<&'b LimitHashSet<T>> for &'a LimitHashSet<T> where
    T: Eq + Hash + Clone, 

type Output = LimitHashSet<T>

The resulting type after applying the - operator.

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

Returns the difference of self and rhs as a new LimitHashSet<T>.

Examples

use nimiq_collections::LimitHashSet;

let a: LimitHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LimitHashSet<_> = 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, 'b, T> BitAnd<&'b LimitHashSet<T>> for &'a LimitHashSet<T> where
    T: Eq + Hash + Clone, 

type Output = LimitHashSet<T>

The resulting type after applying the & operator.

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

Returns the intersection of self and rhs as a new LimitHashSet<T>.

Examples

use nimiq_collections::LimitHashSet;

let a: LimitHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LimitHashSet<_> = 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> BitOr<&'b LimitHashSet<T>> for &'a LimitHashSet<T> where
    T: Eq + Hash + Clone, 

type Output = LimitHashSet<T>

The resulting type after applying the | operator.

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

Returns the union of self and rhs as a new LimitHashSet<T>.

Examples

use nimiq_collections::LimitHashSet;

let a: LimitHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LimitHashSet<_> = 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> BitXor<&'b LimitHashSet<T>> for &'a LimitHashSet<T> where
    T: Eq + Hash + Clone, 

type Output = LimitHashSet<T>

The resulting type after applying the ^ operator.

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

Returns the symmetric difference of self and rhs as a new LimitHashSet<T>.

Examples

use nimiq_collections::LimitHashSet;

let a: LimitHashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: LimitHashSet<_> = 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<T> FromIterator<T> for LimitHashSet<T> where
    T: Eq + Hash, 

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> LimitHashSet<T>

Creates a value from an iterator.