std::collections::hash_set

Enum Entry

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pub enum Entry<'a, T, S> {
    Occupied(OccupiedEntry<'a, T, S>),
    Vacant(VacantEntry<'a, T, S>),
}
🔬This is a nightly-only experimental API. (hash_set_entry #60896)
Expand description

A view into a single entry in a set, which may either be vacant or occupied.

This enum is constructed from the entry method on HashSet.

§Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::HashSet;

let mut set = HashSet::new();
set.extend(["a", "b", "c"]);
assert_eq!(set.len(), 3);

// Existing value (insert)
let entry = set.entry("a");
let _raw_o = entry.insert();
assert_eq!(set.len(), 3);
// Nonexistent value (insert)
set.entry("d").insert();

// Existing value (or_insert)
set.entry("b").or_insert();
// Nonexistent value (or_insert)
set.entry("e").or_insert();

println!("Our HashSet: {:?}", set);

let mut vec: Vec<_> = set.iter().copied().collect();
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, ["a", "b", "c", "d", "e"]);

Variants§

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Occupied(OccupiedEntry<'a, T, S>)

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

An occupied entry.

§Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::{Entry, HashSet};

let mut set = HashSet::from(["a", "b"]);

match set.entry("a") {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(_) => { }
}
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Vacant(VacantEntry<'a, T, S>)

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

A vacant entry.

§Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::{Entry, HashSet};

let mut set = HashSet::new();

match set.entry("a") {
    Entry::Occupied(_) => unreachable!(),
    Entry::Vacant(_) => { }
}

Implementations§

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impl<'a, T, S> Entry<'a, T, S>

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pub fn insert(self) -> OccupiedEntry<'a, T, S>
where T: Hash, S: BuildHasher,

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Sets the value of the entry, and returns an OccupiedEntry.

§Examples
#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();
let entry = set.entry("horseyland").insert();

assert_eq!(entry.get(), &"horseyland");
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pub fn or_insert(self)
where T: Hash, S: BuildHasher,

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Ensures a value is in the entry by inserting if it was vacant.

§Examples
#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();

// nonexistent key
set.entry("poneyland").or_insert();
assert!(set.contains("poneyland"));

// existing key
set.entry("poneyland").or_insert();
assert!(set.contains("poneyland"));
assert_eq!(set.len(), 1);
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pub fn get(&self) -> &T

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Returns a reference to this entry’s value.

§Examples
#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();
set.entry("poneyland").or_insert();

// existing key
assert_eq!(set.entry("poneyland").get(), &"poneyland");
// nonexistent key
assert_eq!(set.entry("horseland").get(), &"horseland");

Trait Implementations§

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impl<T: Debug, S> Debug for Entry<'_, T, S>

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

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<'a, T, S> Freeze for Entry<'a, T, S>
where T: Freeze,

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impl<'a, T, S> RefUnwindSafe for Entry<'a, T, S>

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impl<'a, T, S> Send for Entry<'a, T, S>
where T: Send, S: Send,

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impl<'a, T, S> Sync for Entry<'a, T, S>
where T: Sync, S: Sync,

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impl<'a, T, S> Unpin for Entry<'a, T, S>
where T: Unpin,

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impl<'a, T, S> !UnwindSafe for Entry<'a, T, S>

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.