# has

Check if a value exists in the RefHashSet.

## Signatures

```ts
export declare const has: {
    <V>(value: V): <E, R>(ref: RefHashSet<V, E, R>) => RefSubject.Computed<boolean, E, R>;
    <V, E, R>(ref: RefHashSet<V, E, R>, value: V): RefSubject.Computed<boolean, E, R>;
};
```

## Why

Makes has a live projection of the hash set; consumers can sample it now or observe it without
copying the source state.

## Ownership and lifetime

The has view retains no independent state. An Effect read samples the source once; Fx
observation follows later pushes and its observing Scope owns subscription cleanup.