# Fx.fn

Callable contracts implemented by `fn`.

## Signatures

```ts
export declare namespace fn {
    type Gen = {
        <Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>>(body: (this: unassigned, ...args: Args) => Generator<Eff, ReturnFx>): (...args: Args) => Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>;
        <Self, Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>>(body: (this: Self, ...args: Args) => Generator<Eff, ReturnFx>): (this: Self, ...args: Args) => Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>;
        <Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A>(body: (this: unassigned, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A): (...args: Args) => A;
        <Self, Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A>(body: (this: Self, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A): (this: Self, ...args: Args) => A;
        <Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A, B>(body: (this: unassigned, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A, b: (_: A, ...args: Args) => B): (...args: Args) => B;
        <Self, Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A, B>(body: (this: Self, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A, b: (_: A, ...args: Args) => B): (this: Self, ...args: Args) => B;
        <Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A, B, C>(body: (this: unassigned, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A, b: (_: A, ...args: Args) => B, c: (_: B, ...args: Args) => C): (...args: Args) => C;
        <Self, Eff extends Effect.Effect<any, any, any>, ReturnFx extends Fx.Any, Args extends Array<any>, A, B, C>(body: (this: Self, ...args: Args) => Generator<Eff, ReturnFx>, a: (_: Fx<Fx.Success<ReturnFx>, Fx.Error<ReturnFx> | Effect.Error<Eff>, Fx.Services<ReturnFx> | Effect.Services<Eff>>, ...args: Args) => A, b: (_: A, ...args: Args) => B, c: (_: B, ...args: Args) => C): (this: Self, ...args: Args) => C;
    };
    type NonGen = {
        <Args extends Array<any>, ReturnFx extends Fx.Any>(body: (this: unassigned, ...args: Args) => ReturnFx): (...args: Args) => ReturnFx;
        <Self, Args extends Array<any>, ReturnFx extends Fx.Any>(body: (this: Self, ...args: Args) => ReturnFx): (this: Self, ...args: Args) => ReturnFx;
        <Args extends Array<any>, ReturnFx extends Fx.Any, A>(body: (this: unassigned, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A): (...args: Args) => A;
        <Self, Args extends Array<any>, ReturnFx extends Fx.Any, A>(body: (this: Self, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A): (this: Self, ...args: Args) => A;
        <Args extends Array<any>, ReturnFx extends Fx.Any, A, B>(body: (this: unassigned, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A, b: (_: A, ...args: Args) => B): (...args: Args) => B;
        <Self, Args extends Array<any>, ReturnFx extends Fx.Any, A, B>(body: (this: Self, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A, b: (_: A, ...args: Args) => B): (this: Self, ...args: Args) => B;
        <Args extends Array<any>, ReturnFx extends Fx.Any, A, B, C>(body: (this: unassigned, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A, b: (_: A, ...args: Args) => B, c: (_: B, ...args: Args) => C): (...args: Args) => C;
        <Self, Args extends Array<any>, ReturnFx extends Fx.Any, A, B, C>(body: (this: Self, ...args: Args) => ReturnFx, a: (_: ReturnFx, ...args: Args) => A, b: (_: A, ...args: Args) => B, c: (_: B, ...args: Args) => C): (this: Self, ...args: Args) => C;
    };
}
```

```ts
export declare const fn: fn.Gen & fn.NonGen & {
    (name: string, options?: SpanOptionsNoTrace): fn.Gen & fn.NonGen;
};
```

## Why

The namespace keeps generator and non-generator overload families addressable even
though one callable value implements both.

## Ownership and lifetime

These are type-level contracts. They start no Effect or `Fx` run.

## Examples

```ts
import { Effect } from "effect"
import { Fx } from "@typed/fx"

const request = Fx.fn("request")(
  function* (id: number) {
    const token = yield* Effect.succeed("token")
    return Fx.succeed({ id, token })
  },
  (source) => Fx.map(source, ({ id }) => id)
)
const program = Fx.collectAll(request(42))
```