lattice_crdt

Umbrella package for Lattice CRDTs: counters, registers, sets, maps, and causal core types.

Install this package when you want the full Lattice CRDT toolkit. For smaller dependency graphs, install the individual packages directly.

Installation

gleam add lattice_crdt

Packages included

Package	Provides
`lattice_core`	Replica IDs, version vectors, and dot contexts.
`lattice_counters`	Grow-only and positive-negative counters.
`lattice_registers`	Last-writer-wins and multi-value registers.
`lattice_sets`	Grow-only, two-phase, and observed-remove sets.
`lattice_maps`	Last-writer-wins maps, observed-remove maps, and CRDT dispatch.
`lattice_sequence`	Generic sequence CRDT using YATA-style left/right origins.
`lattice_text`	Plain-text CRDT backed by `lattice_sequence`.

Quick example

import lattice_core/replica_id
import lattice_counters/g_counter

pub fn main() {
  let counter =
    g_counter.new(replica_id.new("node-a"))
    |> g_counter.increment(1)

  g_counter.value(counter)
  // -> 1
}

Notes

This package reuses the public modules from the individual Lattice packages.
Import modules from their package-specific paths, such as lattice_counters/g_counter or lattice_sets/or_set.
All CRDT packages support deterministic merge semantics and JSON serialization.
Many mutators also expose delta-state variants for efficient incremental replication.

Delta-state replication

Every leaf CRDT exposes a delta-state mutator alongside its state-based API. Each op of type T -> args -> T has a companion op_with_delta of type T -> args -> #(T, T) that returns both the new state and a small delta. The delta is itself a value of type T and merges into remote replicas via the existing merge function — there is no separate "apply delta" code path for leaf CRDTs.

ORMap exposes update_with_delta, remove_with_delta, apply_delta, and merge_deltas for the composite case, with a dedicated ORMapDelta type for type safety.

Delta merge is idempotent, commutative, and associative — safe under at-least-once delivery, reconnects, and out-of-order arrival. This makes delta-state CRDTs the natural foundation for websocket-based replication. See DEV.md for the full convention and usage notes, and the examples/or_map_delta_websocket_example.gleam example for a runnable demo of two replicas exchanging deltas.

Reference: Almeida, Shoker, Baquero — Delta State Replicated Data Types.

License

MIT