Struct PersistentHashMap 

pub struct PersistentHashMap { /* private fields */ }

An immutable hash map that preserves insertion order when iterated.

Lookups go through a rpds::HashTrieMap from key to insertion sequence number; the sequence number then indexes a rpds::RedBlackTreeMap that holds the actual (key, value) pairs in insertion order. Re-associating an existing key keeps its original position (matching PersistentArrayMap and how most ordered-map implementations behave), so iteration order is deterministic and matches the order keys were first written, rather than depending on hash-bucket layout (which — since rpds seeds its hasher randomly per instance — would otherwise vary from run to run).

Small maps (≤8 entries) are represented as PersistentArrayMap instead; the two types share the same Value::Map variant. PersistentHashMap is used once the entry count exceeds the array-map threshold.

Implementations

impl PersistentHashMap

pub fn empty() -> Self

pub fn new(map: HashTrieMapSync<Value, Value>) -> Self

Build from a raw HashTrieMap, in its (arbitrary) iteration order.

Prefer from_pairs/assoc when the caller has a meaningful source order to preserve.

pub fn count(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn get(&self, key: &Value) -> Option<&Value>

Look up a key.

pub fn contains_key(&self, key: &Value) -> bool

pub fn assoc(&self, key: Value, value: Value) -> Self

Return a new map with key → value.

Re-associating a key that is already present keeps its original insertion position; a brand-new key is appended at the end.

pub fn dissoc(&self, key: &Value) -> Self

Return a new map with key removed.

pub fn iter(&self) -> impl Iterator<Item = (&Value, &Value)>

Iterate over all (key, value) pairs in insertion order.

pub fn keys(&self) -> Vec<Value>

Collect all keys, in insertion order.

pub fn vals(&self) -> Vec<Value>

Collect all values, in insertion order.

pub fn merge(&self, other: &Self) -> Self

Merge two maps; right-hand side wins on key collision.

pub fn from_pairs<I: IntoIterator<Item = (Value, Value)>>(iter: I) -> Self

Build from an iterator of (key, value) pairs, in the given order.

pub fn from_array_map(am: &PersistentArrayMap) -> Self

Promote from a PersistentArrayMap when the threshold is exceeded.

Trait Implementations

impl Clone for PersistentHashMap

fn clone(&self) -> PersistentHashMap

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PersistentHashMap

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

Formats the value using the given formatter.

impl PartialEq for PersistentHashMap

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Trace for PersistentHashMap

fn trace(&self, visitor: &mut MarkVisitor)

fn gc_size_extra(&self) -> usize