lattice_crdt

lattice_crdt is an umbrella package that re-exports all lattice CRDT sub-packages for convenient dependency management.

Sub-packages

lattice_core — Version vectors, dot contexts, and causal infrastructure
lattice_counters — Grow-only counters (GCounter) and positive-negative counters (PNCounter)
lattice_registers — Last-writer-wins registers (LWWRegister) and multi-value registers (MVRegister)
lattice_sets — Grow-only sets (GSet), two-phase sets (TwoPSet), and observed-remove sets (ORSet)
lattice_maps — Last-writer-wins maps (LWWMap), observed-remove maps (ORMap), and CRDT dispatch
lattice_sequence — Generic sequence CRDT using YATA-style left/right origins
lattice_text — Plain-text CRDT backed by lattice_sequence

Usage

Depend on lattice_crdt to get all sub-packages, or depend on individual sub-packages for minimal dependencies. This module re-exports the primary type from each sub-package so a single import lattice_crdt gives access to the full family of CRDT types; use the sub-package modules directly for their constructors and operations.

// Import from individual sub-packages for constructors and operations:
import lattice_counters/g_counter
import lattice_sets/or_set
import lattice_maps/or_map
import lattice_sequence/sequence
import lattice_text/text

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.

Types

Crdt

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A tagged union over the leaf CRDT types, used for uniform merging.

pub type Crdt =
  crdt.Crdt

CrdtSpec

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A specification used to auto-create default CRDT values for new keys.

pub type CrdtSpec =
  crdt.CrdtSpec

DotContext

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A causal context of observed dots, used by observed-remove CRDTs.

pub type DotContext =
  dot_context.DotContext

GCounter

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A grow-only counter.

pub type GCounter =
  g_counter.GCounter

GSet

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A grow-only set.

pub type GSet(a) =
  g_set.GSet(a)

LWWMap

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A last-writer-wins map.

pub type LWWMap =
  lww_map.LWWMap

LWWRegister

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A last-writer-wins register.

pub type LWWRegister(a) =
  lww_register.LWWRegister(a)

MVRegister

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A multi-value register that preserves concurrent writes.

pub type MVRegister(a) =
  mv_register.MVRegister(a)

ORMap

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An observed-remove map holding heterogeneous CRDT values.

pub type ORMap =
  or_map.ORMap

ORSet

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An observed-remove set.

pub type ORSet(a) =
  or_set.ORSet(a)

PNCounter

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A positive-negative counter composed of two grow-only counters.

pub type PNCounter =
  pn_counter.PNCounter

ReplicaId

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A stable identifier for a replica.

pub type ReplicaId =
  replica_id.ReplicaId

Sequence

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A generic sequence CRDT.

pub type Sequence(a) =
  sequence.Sequence(a)

Text

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A plain-text CRDT backed by a sequence.

pub type Text =
  text.Text

TwoPSet

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A two-phase set supporting removal via a tombstone set.

pub type TwoPSet(a) =
  two_p_set.TwoPSet(a)

VersionVector

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A version vector for tracking causal history across replicas.

pub type VersionVector =
  version_vector.VersionVector