# Fn

---

```text
Fn_class `alias Enum[.partial; .complete; .iterator; .closure; .bound; .regex; .native]

Fn[Fn_class; RETURN_TYPE; ARGS; STATE; List]
```

## \`return

## Transient Union Return Chaining

# Iterating

## \`yield

Yielding wraps the value in the transient union `Next`

Return `Void` to stop iteration

```text
fn : Fn[x] $ ( @ 1 .. x { `yield 2 * x } )
it : fn `sync 10
// invoking
@ it { `log v }[v] // 2 4 6 8 10 12 14 16 18 20
// same as above
@ {
    # `sync it {
        .value { `log v }[v]
        .done { `break }
        .error { `return e }[e]
    }
}
```

# Calling

## \`async

```text
task : `async fn
value : `wait task
```

## \`sync

```text
fn `sync args // `wait fn `async args
```