# RefIterable.contains

Check if a RefIterable contains a value.

## Signatures

```ts
export declare const contains: {
    <A>(value: A): <E, R>(ref: RefIterable<A, E, R>) => RefSubject.Computed<boolean, E, R>;
    <A, E, R>(ref: RefIterable<A, E, R>, value: A): RefSubject.Computed<boolean, E, R>;
};
```

## Why

Makes contains a live projection of the iterable; consumers can sample it now or observe it
without copying the source state.

## Ownership and lifetime

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