persistent

bun add @stopcock/persistent

import { HashMap, Vector } from '@stopcock/persistent'

const original = Vector.of(1, 2, 3)
const updated = original.set(1, 20).push(4)

const users = HashMap.empty<string, { name: string }>()
  .set('ada', { name: 'Ada' })
  .set('grace', { name: 'Grace' })

Ordinary updates never mutate an existing value. Vector uses a 32-way bitmapped trie, hash collections use a HAMT, ordered collections retain insertion order, and queue, deque, and stack use persistent linked spines. Every collection implements Iterable.

For bulk construction, each collection exposes builder() and transient(). Builders mutate private working storage; build() returns an immutable value and permanently seals the builder.

Hash collections use JavaScript Map key semantics by default. Domain equality is opt-in through a coherent HashEq, where equal keys must have equal hashes. Focused subpaths include @stopcock/persistent/vector, @stopcock/persistent/hash-map, @stopcock/persistent/ordered-map, @stopcock/persistent/queue, and their sibling collection modules.