Trait Lookup

pub trait Lookup<Idx, T>: Default {
    // Required methods
    fn len(&self) -> usize;
    fn contains_key(&self, idx: &Idx) -> bool;
    fn get(&self, idx: &Idx) -> Option<&T>;
    fn insert(&mut self, idx: Idx, value: T);
    fn entry_or_insert(&mut self, idx: Idx, value: T) -> &mut T;
    fn values_mut<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T>
       where T: 'a;
    fn iter_mut<'a>(&'a mut self) -> impl Iterator<Item = (&'a Idx, &'a mut T)>
       where T: 'a,
             Idx: 'a;
    fn clear(&mut self);

    // Provided method
    fn is_empty(&self) -> bool { ... }
}

A map of indices to values.

Note that HashMap (with std) or BTreeMap (when no-std) satisfy the requirements and implement the Lookup trait, and hence, can be used as the storage in sparse vectors.

Alternatively, more advanced lookup structures can be provided depending on the use case.

Required Methods

fn len(&self) -> usize

Number of elements stored in the lookup.

fn contains_key(&self, idx: &Idx) -> bool

Returns whether or not the idx is present as a key in the lookup.

fn get(&self, idx: &Idx) -> Option<&T>

Returns a reference to the value with the given idx if it exists in the lookup; returns None otherwise.

fn insert(&mut self, idx: Idx, value: T)

Inserts the value with key idx. If the key already existed, its value is updated.

fn entry_or_insert(&mut self, idx: Idx, value: T) -> &mut T

If the lookup contains an element with the given idx, the method returns a mutable reference to the value.

Otherwise,

• inserts (idx, value) to the lookup, and
• returns a mutable reference to the newly inserted value.

fn values_mut<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T>

where T: 'a,

Returns an iterator yielding mutable references to the values in the lookup.

fn iter_mut<'a>(&'a mut self) -> impl Iterator<Item = (&'a Idx, &'a mut T)>

where T: 'a, Idx: 'a,

Returns an iterator yielding indices and mutable references to the values in the lookup.

fn clear(&mut self)

Clears the lookup.

Provided Methods

fn is_empty(&self) -> bool

Returns true if the lookup is empty.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<Idx: Eq + Hash, T> Lookup<Idx, T> for HashMap<Idx, T>

fn len(&self) -> usize

fn contains_key(&self, idx: &Idx) -> bool

fn get(&self, idx: &Idx) -> Option<&T>

fn insert(&mut self, idx: Idx, value: T)

fn entry_or_insert(&mut self, idx: Idx, value: T) -> &mut T

fn values_mut<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T>

where T: 'a,

fn iter_mut<'a>(&'a mut self) -> impl Iterator<Item = (&'a Idx, &'a mut T)>

where T: 'a, Idx: 'a,

fn clear(&mut self)

impl<Idx: Ord, T> Lookup<Idx, T> for BTreeMap<Idx, T>

fn len(&self) -> usize

fn contains_key(&self, idx: &Idx) -> bool

fn get(&self, idx: &Idx) -> Option<&T>

fn insert(&mut self, idx: Idx, value: T)

fn entry_or_insert(&mut self, idx: Idx, value: T) -> &mut T

fn values_mut<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T>

where T: 'a,

fn iter_mut<'a>(&'a mut self) -> impl Iterator<Item = (&'a Idx, &'a mut T)>

where T: 'a, Idx: 'a,

fn clear(&mut self)

Implementors