@aardworx/wombat.adaptive

TypeScript port of FSharp.Data.Adaptive. Incremental adaptive computations: aval (changeable values), aset (changeable sets), amap (changeable maps), alist (changeable lists), with all the combinators (map / bind / filter / collect / union / sort / pairwise / reduce / …).

The implementation is a faithful port of the F# original — same algorithms, same incremental update semantics, validated against the F# reference impl by 500-run property tests for each adaptive type.

Install

npm install @aardworx/wombat.adaptive

ESM only. Node ≥ 18, modern bundlers (Vite, esbuild, webpack 5+).

Quick start

import { cval, AVal, cset, ASet, transact } from "@aardworx/wombat.adaptive";

const x = cval(1);
const y = cval(2);
const sum = AVal.zip(x, y).map((a, b) => a + b);

console.log(AVal.force(sum)); // 3

transact(() => {
  x.value = 10;
  y.value = 20;
});
console.log(AVal.force(sum)); // 30

const s = cset<number>([1, 2, 3]);
const doubled = ASet.map((n) => n * 2, s);
console.log([...AVal.force(doubled.content)].sort()); // [2, 4, 6]

transact(() => s.add(4));
console.log([...AVal.force(doubled.content)].sort()); // [2, 4, 6, 8]

Module map

The package ships fine-grained sub-paths that all tree-shake well. Pick whichever feels cleaner:

| Sub-path | What it exports | | --- | --- | | @aardworx/wombat.adaptive | Curated public surface — most consumers import from here | | @aardworx/wombat.adaptive/aval | AVal, cval, aval, Reductions | | @aardworx/wombat.adaptive/aset | ASet, cset, aset | | @aardworx/wombat.adaptive/amap | AMap, cmap, amap, KeyValuePair | | @aardworx/wombat.adaptive/alist | AList, clist, alist | | @aardworx/wombat.adaptive/datastructures | HashSet, HashMap, IndexList, Index, MapExt, deltas | | @aardworx/wombat.adaptive/extensions | Cross-collection bridges + addCallback for collections | | @aardworx/wombat.adaptive/traceable | Low-level History / readers (extension authors) | | @aardworx/wombat.adaptive/reference | Slow-but-correct executable spec for property testing |

// fine-grained
import { ASet, cset } from "@aardworx/wombat.adaptive/aset";
import { HashSet } from "@aardworx/wombat.adaptive/datastructures";
import { AListBridges } from "@aardworx/wombat.adaptive/extensions";

Listening to changes

addCallback fires once on subscription with the empty-to-current delta, then on each transaction when the underlying reader has new changes. Mirrors F#'s EvaluationCallbackExtensions.

import { cset, asetCallback, transact } from "@aardworx/wombat.adaptive";

const s = cset<number>([1, 2]);
const sub = asetCallback(s, (state, delta) => {
  console.log("size before:", state.count, "delta size:", delta.count);
});

transact(() => s.add(3));    // logs "size before: 2 delta size: 1"
transact(() => s.remove(1)); // logs "size before: 3 delta size: 1"
sub.dispose();

What's incremental

Every combinator in the public surface is genuinely incremental — applying a delta of size k against a state of size N costs O(k), not O(N), unless k ≥ N (where bulk recompute wins). This includes:

• reduce / reduceBy / reduceByA and everything derived from them: sum, sumBy, sumByA, average, averageBy, fold, foldGroup, foldHalfGroup, forall, exists, forallA, existsA, countBy, countByA, tryMin, tryMax
• contains (refcount-tracked single-value membership)
• map / choose / filter / collect / union / intersect / difference / xor / bind and their *A variants
• AList.range / AList.subA / AList.takeA / AList.skipA (four-region delta merge for shifting integer ranges; overlapping-window delta for slices)

Equality

@aardworx/wombat.adaptive honours the same equals(other) / getHashCode() convention as F#: any object that defines both methods is hashed and compared structurally throughout the library (HashSet keys, HashMap keys, Cache keys, Index identity, etc.). Primitives use Object.is + a type-aware hash.

import { HashSet } from "@aardworx/wombat.adaptive/datastructures";

class Pair {
  constructor(readonly a: number, readonly b: number) {}
  equals(o: unknown): boolean {
    return o instanceof Pair && o.a === this.a && o.b === this.b;
  }
  getHashCode(): number {
    return ((this.a | 0) * 31 + (this.b | 0)) | 0;
  }
}

const s = HashSet.empty<Pair>().add(new Pair(1, 2)).add(new Pair(1, 2));
s.count; // 1

Status

• ✅ Full port of aval / aset / amap / alist and combinators
• ✅ Cross-collection bridges (ASet ↔ AList ↔ AMap)
• ✅ Callbacks with state+delta payloads
• ✅ Reference impl + 500-run property tests for AVal / ASet / AMap / AList
• ⏭️ mapUse / mapUsei (F# uses IDisposable; would map to Symbol.dispose)
• ⏭️ Adaptify codegen (separate library)
• ⏭️ Tree expansion: ASet.ofListTree / ASet.ofSetTree

Build & test

npm install
npm run typecheck   # tsc --noEmit
npm test            # vitest run
npm run build       # emit to dist/

License

MIT — derived from FSharp.Data.Adaptive (© Aardvark Platform).