> For the complete documentation index, see [llms.txt](https://osl.mistium.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://osl.mistium.com/standard-library/utilities/set.md).

# set

Use `set` when you need a collection of unique values with membership checks.

`set` is a built-in language type. It needs no package import.

## Example

```osl
set names = set()
names.add("ada")
log names.contains("ada")
```

## API reference

### `set` values

| Method                   | Returns   | Notes                                     |
| ------------------------ | --------- | ----------------------------------------- |
| `value.add(v: any)`      | `set`     | Adds a comparable value.                  |
| `value.delete(v: any)`   | `error`   | Deletes through the same guard.           |
| `value.contains(v: any)` | `boolean` | Checks membership through the same guard. |
| `value.size()`           | `number`  | Returns the number of stored values.      |
| `value.clear()`          | `void`    | Clears all stored values.                 |
| `value.toArr()`          | `array`   | Converts the value to an array.           |

## Notes

Composite and cyclic values are compared safely. Sets synchronize concurrent reads and writes.