@effect-ts/system/_src/Effect/do.ts

Effect-TS is a zero dependency set of libraries to write highly productive, purely functional TypeScript at scale.

// ets_tracing: off

import { chain_, succeed } from "./core.js"
import type { Effect } from "./effect.js"
import { map_ } from "./map.js"

/**
 * Binds an effectful value in a `do` scope
 *
 * @ets_data_first bind_
 */
function bind<R, E, A, K, N extends string>(
  tag: Exclude<N, keyof K>,
  f: (_: K) => Effect<R, E, A>,
  __trace?: string
) {
  return <R2, E2>(
    mk: Effect<R2, E2, K>
  ): Effect<
    R & R2,
    E | E2,
    K & {
      [k in N]: A
    }
  > => bind_(mk, tag, f, __trace)
}

/**
 * Binds an effectful value in a `do` scope
 */
export function bind_<R2, E2, R, E, A, K, N extends string>(
  mk: Effect<R2, E2, K>,
  tag: Exclude<N, keyof K>,
  f: (_: K) => Effect<R, E, A>,
  __trace?: string
): Effect<
  R & R2,
  E | E2,
  K & {
    [k in N]: A
  }
> {
  return chain_(
    mk,
    (k) =>
      map_(
        f(k),
        (
          a
        ): K & {
          [k in N]: A
        } => ({ ...k, [tag]: a } as any)
      ),
    __trace
  )
}

/**
 * Like bind for values
 *
 * @ets_data_first let_
 */
function let__<A, K, N extends string>(
  tag: Exclude<N, keyof K>,
  f: (_: K) => A,
  __trace?: string
) {
  return <R2, E2>(
    mk: Effect<R2, E2, K>
  ): Effect<
    R2,
    E2,
    K & {
      [k in N]: A
    }
  > => let_(mk, tag, f)
}

/**
 * Like bind for values
 */
export function let_<R2, E2, A, K, N extends string>(
  mk: Effect<R2, E2, K>,
  tag: Exclude<N, keyof K>,
  f: (_: K) => A,
  __trace?: string
): Effect<
  R2,
  E2,
  K & {
    [k in N]: A
  }
> {
  return map_(
    mk,
    (
      k
    ): K & {
      [k in N]: A
    } => ({ ...k, [tag]: f(k) } as any),
    __trace
  )
}

const do_ = succeed({})

export { let__ as let, bind, do_ as do }