lattice_sequence

Generic sequence CRDT for Gleam using YATA-style left/right origins.

Use this package when replicas need to edit a shared ordered list concurrently and converge without coordination. lattice_sequence handles arbitrary element types with index-based insert, delete, and move operations; for a text-specific API with grapheme handling, use lattice_text instead.

Installation

gleam add lattice_sequence

Quick example

import lattice_core/replica_id
import lattice_sequence/sequence

pub fn main() {
  let node_a =
    sequence.new(replica_id.new("node-a"))
    |> sequence.insert(0, "hello")
    |> sequence.insert(1, "world")

  let node_b =
    sequence.new(replica_id.new("node-b"))
    |> sequence.insert(0, "!")

  let merged = sequence.merge(node_a, node_b)

  sequence.values(merged)
  // -> ["hello", "world", "!"]
}

Modules

Module	Purpose
`lattice_sequence/sequence`	Generic list CRDT with stable item IDs, index-based editing, and single-winner move semantics.

Notes

Editing operations: insert, delete, and move.
Query helpers: values and length.
Fallible operations have try_*_with_delta variants returning Result; the plain variants assert on invalid indexes.
Delta-state variants (*_with_delta) return the updated sequence plus a delta that can be merged into other replicas, avoiding full-state sync.
Position anchors: anchor_at (and the start_anchor/end_anchor sentinels) create a stable position that survives concurrent edits and merges, resolve maps it back to a current index, and anchor_to_json/anchor_from_json let anchors travel between replicas (e.g. shared cursors).
compact reclaims space from tombstones and origins once a host-supplied stability frontier confirms no in-flight op can reference them, emitting a ForwardingMap so anchors and rebased ops keep resolving after the region shrinks.
merge, to_json, and from_json round-trip the full CRDT state; convergence holds on both Erlang and JavaScript targets.

License

MIT