effect-io-ai

Package: effect
Module: Result

Result.andThen

Provides a flexible variant of flatMap that accepts multiple input shapes.

When to use

Use to sequence a next step that may be a Result, a function, or a plain value.

Details

The second argument can be:

• A function (a: A) => Result<A2, E2> (same as flatMap)
• A function (a: A) => A2 (auto-wrapped in succeed)
• A Result<A2, E2> value (ignores the success of self)
• A plain value A2 (auto-wrapped in succeed, ignores self)

If self is a Failure, the second argument is never evaluated.

Example (Chaining Result values with different argument types)

import { pipe, Result } from "effect"

// With a function returning a Result
const a = pipe(
  Result.succeed(1),
  Result.andThen((n) => Result.succeed(n + 1))
)

// With a plain mapping function
const b = pipe(
  Result.succeed(1),
  Result.andThen((n) => n + 1)
)

// With a constant value
const c = pipe(Result.succeed(1), Result.andThen("done"))

console.log(a, b, c)

See

• flatMap for the stricter variant (function returning Result only)
• map when you always return a plain value

Signature

declare const andThen: { <A, A2, E2>(f: (a: A) => Result<A2, E2>): <E>(self: Result<A, E>) => Result<A2, E | E2>; <A2, E2>(f: Result<A2, E2>): <A, E>(self: Result<A, E>) => Result<A2, E | E2>; <A, A2>(f: (a: A) => A2): <E>(self: Result<A, E>) => Result<A2, E>; <A2>(right: NotFunction<A2>): <A, E>(self: Result<A, E>) => Result<A2, E>; <A, E, A2, E2>(self: Result<A, E>, f: (a: A) => Result<A2, E2>): Result<A2, E | E2>; <A, E, A2, E2>(self: Result<A, E>, f: Result<A2, E2>): Result<A2, E | E2>; <A, E, A2>(self: Result<A, E>, f: (a: A) => A2): Result<A2, E>; <A, E, A2>(self: Result<A, E>, f: NotFunction<A2>): Result<A2, E>; }

Source

Since v2.0.0