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/** * @since 2.0.0 */ import * as Equivalence from "./Equivalence.js"; import { constNull, constUndefined, dual, identity } from "./Function.js"; import * as doNotation from "./internal/doNotation.js"; import * as either from "./internal/either.js"; import * as option_ from "./internal/option.js"; import { isFunction } from "./Predicate.js"; import * as Gen from "./Utils.js"; /** * @category symbols * @since 2.0.0 */ export const TypeId = either.TypeId; /** * Constructs a new `Either` holding a `Right` value. This usually represents a successful value due to the right bias * of this structure. * * @category constructors * @since 2.0.0 */ export const right = either.right; const void_ = /*#__PURE__*/right(void 0); export { /** * @category constructors * @since 3.13.0 */ void_ as void }; /** * Constructs a new `Either` holding a `Left` value. This usually represents a failure, due to the right-bias of this * structure. * * @category constructors * @since 2.0.0 */ export const left = either.left; /** * Takes a lazy default and a nullable value, if the value is not nully (`null` or `undefined`), turn it into a `Right`, if the value is nully use * the provided default as a `Left`. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.fromNullable(1, () => 'fallback'), Either.right(1)) * assert.deepStrictEqual(Either.fromNullable(null, () => 'fallback'), Either.left('fallback')) * ``` * * @category constructors * @since 2.0.0 */ export const fromNullable = /*#__PURE__*/dual(2, (self, onNullable) => self == null ? left(onNullable(self)) : right(self)); /** * @example * ```ts * import * as assert from "node:assert" * import { Either, Option } from "effect" * * assert.deepStrictEqual(Either.fromOption(Option.some(1), () => 'error'), Either.right(1)) * assert.deepStrictEqual(Either.fromOption(Option.none(), () => 'error'), Either.left('error')) * ``` * * @category constructors * @since 2.0.0 */ export const fromOption = either.fromOption; const try_ = evaluate => { if (isFunction(evaluate)) { try { return right(evaluate()); } catch (e) { return left(e); } } else { try { return right(evaluate.try()); } catch (e) { return left(evaluate.catch(e)); } } }; export { /** * Imports a synchronous side-effect into a pure `Either` value, translating any * thrown exceptions into typed failed eithers creating with `Either.left`. * * @category constructors * @since 2.0.0 */ try_ as try }; /** * Tests if a value is a `Either`. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.isEither(Either.right(1)), true) * assert.deepStrictEqual(Either.isEither(Either.left("a")), true) * assert.deepStrictEqual(Either.isEither({ right: 1 }), false) * ``` * * @category guards * @since 2.0.0 */ export const isEither = either.isEither; /** * Determine if a `Either` is a `Left`. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.isLeft(Either.right(1)), false) * assert.deepStrictEqual(Either.isLeft(Either.left("a")), true) * ``` * * @category guards * @since 2.0.0 */ export const isLeft = either.isLeft; /** * Determine if a `Either` is a `Right`. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.isRight(Either.right(1)), true) * assert.deepStrictEqual(Either.isRight(Either.left("a")), false) * ``` * * @category guards * @since 2.0.0 */ export const isRight = either.isRight; /** * Converts a `Either` to an `Option` discarding the `Left`. * * @example * ```ts * import * as assert from "node:assert" * import { Either, Option } from "effect" * * assert.deepStrictEqual(Either.getRight(Either.right('ok')), Option.some('ok')) * assert.deepStrictEqual(Either.getRight(Either.left('err')), Option.none()) * ``` * * @category getters * @since 2.0.0 */ export const getRight = either.getRight; /** * Converts a `Either` to an `Option` discarding the value. * * @example * ```ts * import * as assert from "node:assert" * import { Either, Option } from "effect" * * assert.deepStrictEqual(Either.getLeft(Either.right('ok')), Option.none()) * assert.deepStrictEqual(Either.getLeft(Either.left('err')), Option.some('err')) * ``` * * @category getters * @since 2.0.0 */ export const getLeft = either.getLeft; /** * @category equivalence * @since 2.0.0 */ export const getEquivalence = ({ left, right }) => Equivalence.make((x, y) => isLeft(x) ? isLeft(y) && left(x.left, y.left) : isRight(y) && right(x.right, y.right)); /** * @category mapping * @since 2.0.0 */ export const mapBoth = /*#__PURE__*/dual(2, (self, { onLeft, onRight }) => isLeft(self) ? left(onLeft(self.left)) : right(onRight(self.right))); /** * Maps the `Left` side of an `Either` value to a new `Either` value. * * @category mapping * @since 2.0.0 */ export const mapLeft = /*#__PURE__*/dual(2, (self, f) => isLeft(self) ? left(f(self.left)) : right(self.right)); /** * Maps the `Right` side of an `Either` value to a new `Either` value. * * @category mapping * @since 2.0.0 */ export const map = /*#__PURE__*/dual(2, (self, f) => isRight(self) ? right(f(self.right)) : left(self.left)); /** * Takes two functions and an `Either` value, if the value is a `Left` the inner value is applied to the `onLeft function, * if the value is a `Right` the inner value is applied to the `onRight` function. * * @example * ```ts * import * as assert from "node:assert" * import { pipe, Either } from "effect" * * const onLeft = (strings: ReadonlyArray<string>): string => `strings: ${strings.join(', ')}` * * const onRight = (value: number): string => `Ok: ${value}` * * assert.deepStrictEqual(pipe(Either.right(1), Either.match({ onLeft, onRight })), 'Ok: 1') * assert.deepStrictEqual( * pipe(Either.left(['string 1', 'string 2']), Either.match({ onLeft, onRight })), * 'strings: string 1, string 2' * ) * ``` * * @category pattern matching * @since 2.0.0 */ export const match = /*#__PURE__*/dual(2, (self, { onLeft, onRight }) => isLeft(self) ? onLeft(self.left) : onRight(self.right)); /** * Transforms a `Predicate` function into a `Right` of the input value if the predicate returns `true` * or `Left` of the result of the provided function if the predicate returns false * * @example * ```ts * import * as assert from "node:assert" * import { pipe, Either } from "effect" * * const isPositive = (n: number): boolean => n > 0 * const isPositiveEither = Either.liftPredicate(isPositive, n => `${n} is not positive`) * * assert.deepStrictEqual( * isPositiveEither(1), * Either.right(1) * ) * assert.deepStrictEqual( * isPositiveEither(0), * Either.left("0 is not positive") * ) * ``` * * @category lifting * @since 3.4.0 */ export const liftPredicate = /*#__PURE__*/dual(3, (a, predicate, orLeftWith) => predicate(a) ? right(a) : left(orLeftWith(a))); /** * Filter the right value with the provided function. * If the predicate fails, set the left value with the result of the provided function. * * @example * ```ts * import * as assert from "node:assert" * import { pipe, Either } from "effect" * * const isPositive = (n: number): boolean => n > 0 * * assert.deepStrictEqual( * pipe( * Either.right(1), * Either.filterOrLeft(isPositive, n => `${n} is not positive`) * ), * Either.right(1) * ) * assert.deepStrictEqual( * pipe( * Either.right(0), * Either.filterOrLeft(isPositive, n => `${n} is not positive`) * ), * Either.left("0 is not positive") * ) * ``` * * @since 2.0.0 * @category filtering & conditionals */ export const filterOrLeft = /*#__PURE__*/dual(3, (self, predicate, orLeftWith) => flatMap(self, r => predicate(r) ? right(r) : left(orLeftWith(r)))); /** * @category getters * @since 2.0.0 */ export const merge = /*#__PURE__*/match({ onLeft: identity, onRight: identity }); /** * Returns the wrapped value if it's a `Right` or a default value if is a `Left`. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.getOrElse(Either.right(1), (error) => error + "!"), 1) * assert.deepStrictEqual(Either.getOrElse(Either.left("not a number"), (error) => error + "!"), "not a number!") * ``` * * @category getters * @since 2.0.0 */ export const getOrElse = /*#__PURE__*/dual(2, (self, onLeft) => isLeft(self) ? onLeft(self.left) : self.right); /** * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.getOrNull(Either.right(1)), 1) * assert.deepStrictEqual(Either.getOrNull(Either.left("a")), null) * ``` * * @category getters * @since 2.0.0 */ export const getOrNull = /*#__PURE__*/getOrElse(constNull); /** * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.getOrUndefined(Either.right(1)), 1) * assert.deepStrictEqual(Either.getOrUndefined(Either.left("a")), undefined) * ``` * * @category getters * @since 2.0.0 */ export const getOrUndefined = /*#__PURE__*/getOrElse(constUndefined); /** * Extracts the value of an `Either` or throws if the `Either` is `Left`. * * If a default error is sufficient for your use case and you don't need to configure the thrown error, see {@link getOrThrow}. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual( * Either.getOrThrowWith(Either.right(1), () => new Error('Unexpected Left')), * 1 * ) * assert.throws(() => Either.getOrThrowWith(Either.left("error"), () => new Error('Unexpected Left'))) * ``` * * @category getters * @since 2.0.0 */ export const getOrThrowWith = /*#__PURE__*/dual(2, (self, onLeft) => { if (isRight(self)) { return self.right; } throw onLeft(self.left); }); // TODO(4.0): by default should throw `L` (i.e getOrThrowWith with the identity function) /** * Extracts the value of an `Either` or throws if the `Either` is `Left`. * * The thrown error is a default error. To configure the error thrown, see {@link getOrThrowWith}. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.getOrThrow(Either.right(1)), 1) * assert.throws(() => Either.getOrThrow(Either.left("error"))) * ``` * * @throws `Error("getOrThrow called on a Left")` * * @category getters * @since 2.0.0 */ export const getOrThrow = /*#__PURE__*/getOrThrowWith(() => new Error("getOrThrow called on a Left")); /** * Returns `self` if it is a `Right` or `that` otherwise. * * @category error handling * @since 2.0.0 */ export const orElse = /*#__PURE__*/dual(2, (self, that) => isLeft(self) ? that(self.left) : right(self.right)); /** * @category sequencing * @since 2.0.0 */ export const flatMap = /*#__PURE__*/dual(2, (self, f) => isLeft(self) ? left(self.left) : f(self.right)); /** * Executes a sequence of two `Either`s. The second `Either` can be dependent on the result of the first `Either`. * * @category sequencing * @since 2.0.0 */ export const andThen = /*#__PURE__*/dual(2, (self, f) => flatMap(self, a => { const b = isFunction(f) ? f(a) : f; return isEither(b) ? b : right(b); })); /** * @category zipping * @since 2.0.0 */ export const zipWith = /*#__PURE__*/dual(3, (self, that, f) => flatMap(self, r => map(that, r2 => f(r, r2)))); /** * @category combining * @since 2.0.0 */ export const ap = /*#__PURE__*/dual(2, (self, that) => zipWith(self, that, (f, a) => f(a))); /** * Takes a structure of `Either`s and returns an `Either` of values with the same structure. * * - If a tuple is supplied, then the returned `Either` will contain a tuple with the same length. * - If a struct is supplied, then the returned `Either` will contain a struct with the same keys. * - If an iterable is supplied, then the returned `Either` will contain an array. * * @example * ```ts * import * as assert from "node:assert" * import { Either } from "effect" * * assert.deepStrictEqual(Either.all([Either.right(1), Either.right(2)]), Either.right([1, 2])) * assert.deepStrictEqual(Either.all({ right: Either.right(1), b: Either.right("hello") }), Either.right({ right: 1, b: "hello" })) * assert.deepStrictEqual(Either.all({ right: Either.right(1), b: Either.left("error") }), Either.left("error")) * ``` * * @category combining * @since 2.0.0 */ // @ts-expect-error export const all = input => { if (Symbol.iterator in input) { const out = []; for (const e of input) { if (isLeft(e)) { return e; } out.push(e.right); } return right(out); } const out = {}; for (const key of Object.keys(input)) { const e = input[key]; if (isLeft(e)) { return e; } out[key] = e.right; } return right(out); }; /** * Returns an `Either` that swaps the error/success cases. This allows you to * use all methods on the error channel, possibly before flipping back. * * @since 2.0.0 * @category mapping */ export const flip = self => isLeft(self) ? right(self.left) : left(self.right); const adapter = /*#__PURE__*/Gen.adapter(); /** * @category generators * @since 2.0.0 */ export const gen = (...args) => { const f = args.length === 1 ? args[0] : args[1].bind(args[0]); const iterator = f(adapter); let state = iterator.next(); while (!state.done) { const current = Gen.isGenKind(state.value) ? state.value.value : Gen.yieldWrapGet(state.value); if (isLeft(current)) { return current; } state = iterator.next(current.right); } return right(state.value); }; // ------------------------------------------------------------------------------------- // do notation // ------------------------------------------------------------------------------------- /** * The "do simulation" in Effect allows you to write code in a more declarative style, similar to the "do notation" in other programming languages. It provides a way to define variables and perform operations on them using functions like `bind` and `let`. * * Here's how the do simulation works: * * 1. Start the do simulation using the `Do` value * 2. Within the do simulation scope, you can use the `bind` function to define variables and bind them to `Either` values * 3. You can accumulate multiple `bind` statements to define multiple variables within the scope * 4. Inside the do simulation scope, you can also use the `let` function to define variables and bind them to simple values * * @example * ```ts * import * as assert from "node:assert" * import { Either, pipe } from "effect" * * const result = pipe( * Either.Do, * Either.bind("x", () => Either.right(2)), * Either.bind("y", () => Either.right(3)), * Either.let("sum", ({ x, y }) => x + y) * ) * assert.deepStrictEqual(result, Either.right({ x: 2, y: 3, sum: 5 })) * ``` * * @see {@link bind} * @see {@link bindTo} * @see {@link let_ let} * * @category do notation * @since 2.0.0 */ export const Do = /*#__PURE__*/right({}); /** * The "do simulation" in Effect allows you to write code in a more declarative style, similar to the "do notation" in other programming languages. It provides a way to define variables and perform operations on them using functions like `bind` and `let`. * * Here's how the do simulation works: * * 1. Start the do simulation using the `Do` value * 2. Within the do simulation scope, you can use the `bind` function to define variables and bind them to `Either` values * 3. You can accumulate multiple `bind` statements to define multiple variables within the scope * 4. Inside the do simulation scope, you can also use the `let` function to define variables and bind them to simple values * * @example * ```ts * import * as assert from "node:assert" * import { Either, pipe } from "effect" * * const result = pipe( * Either.Do, * Either.bind("x", () => Either.right(2)), * Either.bind("y", () => Either.right(3)), * Either.let("sum", ({ x, y }) => x + y) * ) * assert.deepStrictEqual(result, Either.right({ x: 2, y: 3, sum: 5 })) * ``` * * @see {@link Do} * @see {@link bindTo} * @see {@link let_ let} * * @category do notation * @since 2.0.0 */ export const bind = /*#__PURE__*/doNotation.bind(map, flatMap); /** * The "do simulation" in Effect allows you to write code in a more declarative style, similar to the "do notation" in other programming languages. It provides a way to define variables and perform operations on them using functions like `bind` and `let`. * * Here's how the do simulation works: * * 1. Start the do simulation using the `Do` value * 2. Within the do simulation scope, you can use the `bind` function to define variables and bind them to `Either` values * 3. You can accumulate multiple `bind` statements to define multiple variables within the scope * 4. Inside the do simulation scope, you can also use the `let` function to define variables and bind them to simple values * * @example * ```ts * import * as assert from "node:assert" * import { Either, pipe } from "effect" * * const result = pipe( * Either.Do, * Either.bind("x", () => Either.right(2)), * Either.bind("y", () => Either.right(3)), * Either.let("sum", ({ x, y }) => x + y) * ) * assert.deepStrictEqual(result, Either.right({ x: 2, y: 3, sum: 5 })) * ``` * * @see {@link Do} * @see {@link bind} * @see {@link let_ let} * * @category do notation * @since 2.0.0 */ export const bindTo = /*#__PURE__*/doNotation.bindTo(map); const let_ = /*#__PURE__*/doNotation.let_(map); export { /** * The "do simulation" in Effect allows you to write code in a more declarative style, similar to the "do notation" in other programming languages. It provides a way to define variables and perform operations on them using functions like `bind` and `let`. * * Here's how the do simulation works: * * 1. Start the do simulation using the `Do` value * 2. Within the do simulation scope, you can use the `bind` function to define variables and bind them to `Either` values * 3. You can accumulate multiple `bind` statements to define multiple variables within the scope * 4. Inside the do simulation scope, you can also use the `let` function to define variables and bind them to simple values * * @example * ```ts * import * as assert from "node:assert" * import { Either, pipe } from "effect" * * const result = pipe( * Either.Do, * Either.bind("x", () => Either.right(2)), * Either.bind("y", () => Either.right(3)), * Either.let("sum", ({ x, y }) => x + y) * ) * assert.deepStrictEqual(result, Either.right({ x: 2, y: 3, sum: 5 })) * ``` * * @see {@link Do} * @see {@link bindTo} * @see {@link bind} * * @category do notation * @since 2.0.0 */ let_ as let }; /** * Converts an `Option` of an `Either` into an `Either` of an `Option`. * * **Details** * * This function transforms an `Option<Either<A, E>>` into an * `Either<Option<A>, E>`. If the `Option` is `None`, the resulting `Either` * will be a `Right` with a `None` value. If the `Option` is `Some`, the * inner `Either` will be executed, and its result wrapped in a `Some`. * * @example * ```ts * import { Effect, Either, Option } from "effect" * * // ┌─── Option<Either<number, never>> * // ▼ * const maybe = Option.some(Either.right(42)) * * // ┌─── Either<Option<number>, never, never> * // ▼ * const result = Either.transposeOption(maybe) * * console.log(Effect.runSync(result)) * // Output: { _id: 'Option', _tag: 'Some', value: 42 } * ``` * * @since 3.14.0 * @category Optional Wrapping & Unwrapping */ export const transposeOption = self => { return option_.isNone(self) ? right(option_.none) : map(self.value, option_.some); }; /** * Applies an `Either` on an `Option` and transposes the result. * * **Details** * * If the `Option` is `None`, the resulting `Either` will immediately succeed with a `Right` value of `None`. * If the `Option` is `Some`, the transformation function will be applied to the inner value, and its result wrapped in a `Some`. * * @example * ```ts * import { Either, Option, pipe } from "effect" * * // ┌─── Either<Option<number>, never>> * // ▼ * const noneResult = pipe( * Option.none(), * Either.transposeMapOption(() => Either.right(42)) // will not be executed * ) * console.log(noneResult) * // Output: { _id: 'Either', _tag: 'Right', right: { _id: 'Option', _tag: 'None' } } * * // ┌─── Either<Option<number>, never>> * // ▼ * const someRightResult = pipe( * Option.some(42), * Either.transposeMapOption((value) => Either.right(value * 2)) * ) * console.log(someRightResult) * // Output: { _id: 'Either', _tag: 'Right', right: { _id: 'Option', _tag: 'Some', value: 84 } } * ``` * * @since 3.15.0 * @category Optional Wrapping & Unwrapping */ export const transposeMapOption = /*#__PURE__*/dual(2, (self, f) => option_.isNone(self) ? right(option_.none) : map(f(self.value), option_.some)); //# sourceMappingURL=Either.js.map