# RefString.concat

Concatenate a string to the current state of a RefString.

## Signatures

```ts
export declare const concat: {
    (that: string): <E, R>(ref: RefString<E, R>) => RefSubject.Computed<string, E, R>;
    <E, R>(ref: RefString<E, R>, that: string): RefSubject.Computed<string, E, R>;
};
```

## Why

Concatenate a string to the current state of a RefString. The operation remains attached to the
RefSubject's versioned state boundary.

## Ownership and lifetime

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