# Plus

```
interface Plus<F> extends Alt<F> {
readonly zero: <A>() => HKT<F, A>
}
```

Added in v1.0.0 (type class)

The `Plus`

type class extends the Alt type class with a value that should be the left and right identity for `alt`

.

It is similar to Monoid, except that it applies to types of kind `* -> *`

, like Array or Option, rather than
concrete types like `string`

or `number`

.

`Plus`

instances should satisfy the following laws:

- Left identity:
`A.alt(zero, fa) == fa`

- Right identity:
`A.alt(fa, zero) == fa`

- Annihilation:
`A.map(zero, fa) == zero`