# map

Map (Endomorphic) the values of a RefChunk.

## Signatures

```ts
export declare const map: {
    <A>(f: (a: A, index: number) => A): <E, R>(ref: RefChunk<A, E, R>) => Effect.Effect<Chunk.Chunk<A>, E, R>;
    <A, E, R>(ref: RefChunk<A, E, R>, f: (a: A, index: number) => A): Effect.Effect<Chunk.Chunk<A>, E, R>;
};
```

## Why

Applies map to the committed chunk through `RefSubject.update` and publishes one coherent
replacement; this is a mutation, not a read-only Computed projection.

## Ownership and lifetime

The Effect starts when run, participates in the source ref's serialized update boundary, and
acquires no resource. It returns the committed chunk and retains the ref's E and R channels.