# Fn

---

```text
Fn_class `alias Enum[.unknown; .incomplete; .process; .generator; .iterator; .closure; .bound; .regex; .native]

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

# Function Classes

## Unknown

Placeholder before evaluation

## Incomplete

A function with an incomplete type, type checking occurs at invocation

## Process

A list of tasks with state

## Generator

A function for creating an iterator or closure

## Iterator

A task creator with state, cannot take arguments, can be called until done

## Closure

A task creator with state that can take arguments

## Bound

A function with some arguments already set

## Regex

Regular Expression

## Native

Native function wrapper

# Returning

## \`return

## Transient Union Return Chaining

# Iterating

## \`yield

Yielding wraps the value in the transient union `Next`

Return `Void` to stop iteration

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

# Calling

## \`fork

```text
task : `fork fn
value : `join task
```

## \`call

```text
fn `call args // `join fn `task args
```