effect-io-ai

Package: effect
Module: Utils

Utils.Gen

Type-level signature for generator-based monadic composition over any TypeLambda.

When to use

Use to type the gen function of a module that supports generator syntax, such as Option.gen, Result.gen, and Effect.gen.

Details

This is a pure type alias with no runtime behavior. It infers R, O, and E from the yielded values via Variance or Kind constraints. The generator’s return type A becomes the output’s A parameter.

Example (Typing a gen function for Option)

import type { Option, Utils } from "effect"

declare const gen: Utils.Gen<Option.OptionTypeLambda>

See

• Variance for encoding the variance used for inference
• SingleShotGen for the iterator protocol that makes yielding work

Signature

type Gen<F> = <
  Self,
  K extends Variance<F, any, any, any> | Kind<F, any, any, any, any>,
  A
>(
  ...args:
    | [
      self: Self,
      body: (this: Self) => Generator<K, A, never>
    ]
    | [
      body: () => Generator<K, A, never>
    ]
) => Kind<
  F,
  [K] extends [Variance<F, infer R, any, any>] ? R
    : [K] extends [Kind<F, infer R, any, any, any>] ? R
    : never,
  [K] extends [Variance<F, any, infer O, any>] ? O
    : [K] extends [Kind<F, any, infer O, any, any>] ? O
    : never,
  [K] extends [Variance<F, any, any, infer E>] ? E
    : [K] extends [Kind<F, any, any, infer E, any>] ? E
    : never,
  A
>

Source

Since v2.0.0