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Option.ts•132 kB
/**
* @since 2.0.0
*/
import type { Either } from "./Either.js"
import * as Equal from "./Equal.js"
import * as Equivalence from "./Equivalence.js"
import type { LazyArg } from "./Function.js"
import { constNull, constUndefined, dual, identity, isFunction } from "./Function.js"
import type { TypeLambda } from "./HKT.js"
import type { Inspectable } from "./Inspectable.js"
import * as doNotation from "./internal/doNotation.js"
import * as either from "./internal/either.js"
import * as option from "./internal/option.js"
import type { Order } from "./Order.js"
import * as order from "./Order.js"
import type { Pipeable } from "./Pipeable.js"
import type { Predicate, Refinement } from "./Predicate.js"
import type { Covariant, NoInfer, NotFunction } from "./Types.js"
import type * as Unify from "./Unify.js"
import * as Gen from "./Utils.js"
/**
* The `Option` data type represents optional values. An `Option<A>` can either
* be `Some<A>`, containing a value of type `A`, or `None`, representing the
* absence of a value.
*
* **When to Use**
*
* You can use `Option` in scenarios like:
*
* - Using it for initial values
* - Returning values from functions that are not defined for all possible
* inputs (referred to as “partial functions”)
* - Managing optional fields in data structures
* - Handling optional function arguments
*
* @category Models
* @since 2.0.0
*/
export type Option<A> = None<A> | Some<A>
/**
* @category Symbols
* @since 2.0.0
*/
export const TypeId: unique symbol = Symbol.for("effect/Option")
/**
* @category Symbols
* @since 2.0.0
*/
export type TypeId = typeof TypeId
/**
* @category Models
* @since 2.0.0
*/
export interface None<out A> extends Pipeable, Inspectable {
readonly _tag: "None"
readonly _op: "None"
readonly [TypeId]: {
readonly _A: Covariant<A>
}
[Unify.typeSymbol]?: unknown
[Unify.unifySymbol]?: OptionUnify<this>
[Unify.ignoreSymbol]?: OptionUnifyIgnore
}
/**
* @category Models
* @since 2.0.0
*/
export interface Some<out A> extends Pipeable, Inspectable {
readonly _tag: "Some"
readonly _op: "Some"
readonly value: A
readonly [TypeId]: {
readonly _A: Covariant<A>
}
[Unify.typeSymbol]?: unknown
[Unify.unifySymbol]?: OptionUnify<this>
[Unify.ignoreSymbol]?: OptionUnifyIgnore
}
/**
* @category Models
* @since 2.0.0
*/
export interface OptionUnify<A extends { [Unify.typeSymbol]?: any }> {
Option?: () => A[Unify.typeSymbol] extends Option<infer A0> | infer _ ? Option<A0> : never
}
/**
* @since 2.0.0
*/
export declare namespace Option {
/**
* Extracts the type of the value contained in an `Option`.
*
* **Example** (Getting the Value Type of an Option)
*
* ```ts
* import { Option } from "effect"
*
* // Declare an Option holding a string
* declare const myOption: Option.Option<string>
*
* // Extract the type of the value within the Option
* //
* // ┌─── string
* // ▼
* type MyType = Option.Option.Value<typeof myOption>
* ```
*
* @since 2.0.0
* @category Type-level Utils
*/
export type Value<T extends Option<any>> = [T] extends [Option<infer _A>] ? _A : never
}
/**
* @category Models
* @since 2.0.0
*/
export interface OptionUnifyIgnore {}
/**
* @category Type Lambdas
* @since 2.0.0
*/
export interface OptionTypeLambda extends TypeLambda {
readonly type: Option<this["Target"]>
}
/**
* Represents the absence of a value by creating an empty `Option`.
*
* `Option.none` returns an `Option<never>`, which is a subtype of `Option<A>`.
* This means you can use it in place of any `Option<A>` regardless of the type
* `A`.
*
* **Example** (Creating an Option with No Value)
*
* ```ts
* import { Option } from "effect"
*
* // An Option holding no value
* //
* // ┌─── Option<never>
* // ▼
* const noValue = Option.none()
*
* console.log(noValue)
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @see {@link some} for the opposite operation.
*
* @category Constructors
* @since 2.0.0
*/
export const none = <A = never>(): Option<A> => option.none
/**
* Wraps the given value into an `Option` to represent its presence.
*
* **Example** (Creating an Option with a Value)
*
* ```ts
* import { Option } from "effect"
*
* // An Option holding the number 1
* //
* // ┌─── Option<number>
* // ▼
* const value = Option.some(1)
*
* console.log(value)
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
* ```
*
* @see {@link none} for the opposite operation.
*
* @category Constructors
* @since 2.0.0
*/
export const some: <A>(value: A) => Option<A> = option.some
/**
* Determines whether the given value is an `Option`.
*
* **Details**
*
* This function checks if a value is an instance of `Option`. It returns `true`
* if the value is either `Option.some` or `Option.none`, and `false` otherwise.
* This is particularly useful when working with unknown values or when you need
* to ensure type safety in your code.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.isOption(Option.some(1)))
* // Output: true
*
* console.log(Option.isOption(Option.none()))
* // Output: true
*
* console.log(Option.isOption({}))
* // Output: false
* ```
*
* @category Guards
* @since 2.0.0
*/
export const isOption: (input: unknown) => input is Option<unknown> = option.isOption
/**
* Checks whether an `Option` represents the absence of a value (`None`).
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.isNone(Option.some(1)))
* // Output: false
*
* console.log(Option.isNone(Option.none()))
* // Output: true
* ```
*
* @see {@link isSome} for the opposite check.
*
* @category Guards
* @since 2.0.0
*/
export const isNone: <A>(self: Option<A>) => self is None<A> = option.isNone
/**
* Checks whether an `Option` contains a value (`Some`).
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.isSome(Option.some(1)))
* // Output: true
*
* console.log(Option.isSome(Option.none()))
* // Output: false
* ```
*
* @see {@link isNone} for the opposite check.
*
* @category Guards
* @since 2.0.0
*/
export const isSome: <A>(self: Option<A>) => self is Some<A> = option.isSome
/**
* Performs pattern matching on an `Option` to handle both `Some` and `None`
* cases.
*
* **Details**
*
* This function allows you to match against an `Option` and handle both
* scenarios: when the `Option` is `None` (i.e., contains no value), and when
* the `Option` is `Some` (i.e., contains a value). It executes one of the
* provided functions based on the case:
*
* - If the `Option` is `None`, the `onNone` function is executed and its result
* is returned.
* - If the `Option` is `Some`, the `onSome` function is executed with the
* contained value, and its result is returned.
*
* This function provides a concise and functional way to handle optional values
* without resorting to `if` or manual checks, making your code more declarative
* and readable.
*
* **Example** (Pattern Matching with Option)
*
* ```ts
* import { Option } from "effect"
*
* const foo = Option.some(1)
*
* const message = Option.match(foo, {
* onNone: () => "Option is empty",
* onSome: (value) => `Option has a value: ${value}`
* })
*
* console.log(message)
* // Output: "Option has a value: 1"
* ```
*
* @category Pattern matching
* @since 2.0.0
*/
export const match: {
/**
* Performs pattern matching on an `Option` to handle both `Some` and `None`
* cases.
*
* **Details**
*
* This function allows you to match against an `Option` and handle both
* scenarios: when the `Option` is `None` (i.e., contains no value), and when
* the `Option` is `Some` (i.e., contains a value). It executes one of the
* provided functions based on the case:
*
* - If the `Option` is `None`, the `onNone` function is executed and its result
* is returned.
* - If the `Option` is `Some`, the `onSome` function is executed with the
* contained value, and its result is returned.
*
* This function provides a concise and functional way to handle optional values
* without resorting to `if` or manual checks, making your code more declarative
* and readable.
*
* **Example** (Pattern Matching with Option)
*
* ```ts
* import { Option } from "effect"
*
* const foo = Option.some(1)
*
* const message = Option.match(foo, {
* onNone: () => "Option is empty",
* onSome: (value) => `Option has a value: ${value}`
* })
*
* console.log(message)
* // Output: "Option has a value: 1"
* ```
*
* @category Pattern matching
* @since 2.0.0
*/
<B, A, C = B>(
options: {
readonly onNone: LazyArg<B>
readonly onSome: (a: A) => C
}
): (self: Option<A>) => B | C
/**
* Performs pattern matching on an `Option` to handle both `Some` and `None`
* cases.
*
* **Details**
*
* This function allows you to match against an `Option` and handle both
* scenarios: when the `Option` is `None` (i.e., contains no value), and when
* the `Option` is `Some` (i.e., contains a value). It executes one of the
* provided functions based on the case:
*
* - If the `Option` is `None`, the `onNone` function is executed and its result
* is returned.
* - If the `Option` is `Some`, the `onSome` function is executed with the
* contained value, and its result is returned.
*
* This function provides a concise and functional way to handle optional values
* without resorting to `if` or manual checks, making your code more declarative
* and readable.
*
* **Example** (Pattern Matching with Option)
*
* ```ts
* import { Option } from "effect"
*
* const foo = Option.some(1)
*
* const message = Option.match(foo, {
* onNone: () => "Option is empty",
* onSome: (value) => `Option has a value: ${value}`
* })
*
* console.log(message)
* // Output: "Option has a value: 1"
* ```
*
* @category Pattern matching
* @since 2.0.0
*/
<A, B, C = B>(
self: Option<A>,
options: {
readonly onNone: LazyArg<B>
readonly onSome: (a: A) => C
}
): B | C
} = dual(
2,
<A, B, C = B>(self: Option<A>, { onNone, onSome }: {
readonly onNone: LazyArg<B>
readonly onSome: (a: A) => C
}): B | C => isNone(self) ? onNone() : onSome(self.value)
)
/**
* Converts an `Option`-returning function into a type guard.
*
* **Details**
*
* This function transforms a function that returns an `Option` into a type
* guard, ensuring type safety when validating or narrowing types. The returned
* type guard function checks whether the input satisfies the condition defined
* in the original `Option`-returning function.
*
* If the original function returns `Option.some`, the type guard evaluates to
* `true`, confirming the input is of the desired type. If the function returns
* `Option.none`, the type guard evaluates to `false`.
*
* This utility is especially useful for validating types in union types,
* filtering arrays, or ensuring safe handling of specific subtypes.
*
* @example
* ```ts
* import { Option } from "effect"
*
* type MyData = string | number
*
* const parseString = (data: MyData): Option.Option<string> =>
* typeof data === "string" ? Option.some(data) : Option.none()
*
* // ┌─── (a: MyData) => a is string
* // ▼
* const isString = Option.toRefinement(parseString)
*
* console.log(isString("a"))
* // Output: true
*
* console.log(isString(1))
* // Output: false
* ```
*
* @category Conversions
* @since 2.0.0
*/
export const toRefinement = <A, B extends A>(f: (a: A) => Option<B>): (a: A) => a is B => (a: A): a is B => isSome(f(a))
/**
* Converts an `Iterable` into an `Option`, wrapping the first element if it
* exists.
*
* **Details**
*
* This function takes an `Iterable` (e.g., an array, a generator, or any object
* implementing the `Iterable` interface) and returns an `Option` based on its
* content:
*
* - If the `Iterable` contains at least one element, the first element is
* wrapped in a `Some` and returned.
* - If the `Iterable` is empty, `None` is returned, representing the absence of
* a value.
*
* This utility is useful for safely handling collections that might be empty,
* ensuring you explicitly handle both cases where a value exists or doesn't.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.fromIterable([1, 2, 3]))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(Option.fromIterable([]))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Constructors
* @since 2.0.0
*/
export const fromIterable = <A>(collection: Iterable<A>): Option<A> => {
for (const a of collection) {
return some(a)
}
return none()
}
/**
* Converts an `Either` into an `Option` by discarding the error and extracting
* the right value.
*
* **Details**
*
* This function takes an `Either` and returns an `Option` based on its value:
*
* - If the `Either` is a `Right`, its value is wrapped in a `Some` and
* returned.
* - If the `Either` is a `Left`, the error is discarded, and `None` is
* returned.
*
* This is particularly useful when you only care about the success case
* (`Right`) of an `Either` and want to handle the result using `Option`. By
* using this function, you can convert `Either` into a simpler structure for
* cases where error handling is not required.
*
* @example
* ```ts
* import { Either, Option } from "effect"
*
* console.log(Option.getRight(Either.right("ok")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'ok' }
*
* console.log(Option.getRight(Either.left("err")))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @see {@link getLeft} for the opposite operation.
*
* @category Conversions
* @since 2.0.0
*/
export const getRight: <R, L>(self: Either<R, L>) => Option<R> = either.getRight
/**
* Converts an `Either` into an `Option` by discarding the right value and
* extracting the left value.
*
* **Details**
*
* This function transforms an `Either` into an `Option` as follows:
*
* - If the `Either` is a `Left`, its value is wrapped in a `Some` and returned.
* - If the `Either` is a `Right`, the value is discarded, and `None` is
* returned.
*
* This utility is useful when you only care about the error case (`Left`) of an
* `Either` and want to handle it as an `Option`. By discarding the right value,
* it simplifies error-focused workflows.
*
* @example
* ```ts
* import { Either, Option } from "effect"
*
* console.log(Option.getLeft(Either.right("ok")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.getLeft(Either.left("err")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'err' }
* ```
*
* @see {@link getRight} for the opposite operation.
*
* @category Conversions
* @since 2.0.0
*/
export const getLeft: <R, L>(self: Either<R, L>) => Option<L> = either.getLeft
/**
* Returns the value contained in the `Option` if it is `Some`, otherwise
* evaluates and returns the result of `onNone`.
*
* **Details**
*
* This function allows you to provide a fallback value or computation for when
* an `Option` is `None`. If the `Option` contains a value (`Some`), that value
* is returned. If it is empty (`None`), the `onNone` function is executed, and
* its result is returned instead.
*
* This utility is helpful for safely handling `Option` values by ensuring you
* always receive a meaningful result, whether or not the `Option` contains a
* value. It is particularly useful for providing default values or alternative
* logic when working with optional values.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(1).pipe(Option.getOrElse(() => 0)))
* // Output: 1
*
* console.log(Option.none().pipe(Option.getOrElse(() => 0)))
* // Output: 0
* ```
*
* @see {@link getOrNull} for a version that returns `null` instead of executing a function.
* @see {@link getOrUndefined} for a version that returns `undefined` instead of executing a function.
*
* @category Getters
* @since 2.0.0
*/
export const getOrElse: {
/**
* Returns the value contained in the `Option` if it is `Some`, otherwise
* evaluates and returns the result of `onNone`.
*
* **Details**
*
* This function allows you to provide a fallback value or computation for when
* an `Option` is `None`. If the `Option` contains a value (`Some`), that value
* is returned. If it is empty (`None`), the `onNone` function is executed, and
* its result is returned instead.
*
* This utility is helpful for safely handling `Option` values by ensuring you
* always receive a meaningful result, whether or not the `Option` contains a
* value. It is particularly useful for providing default values or alternative
* logic when working with optional values.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(1).pipe(Option.getOrElse(() => 0)))
* // Output: 1
*
* console.log(Option.none().pipe(Option.getOrElse(() => 0)))
* // Output: 0
* ```
*
* @see {@link getOrNull} for a version that returns `null` instead of executing a function.
* @see {@link getOrUndefined} for a version that returns `undefined` instead of executing a function.
*
* @category Getters
* @since 2.0.0
*/
<B>(onNone: LazyArg<B>): <A>(self: Option<A>) => B | A
/**
* Returns the value contained in the `Option` if it is `Some`, otherwise
* evaluates and returns the result of `onNone`.
*
* **Details**
*
* This function allows you to provide a fallback value or computation for when
* an `Option` is `None`. If the `Option` contains a value (`Some`), that value
* is returned. If it is empty (`None`), the `onNone` function is executed, and
* its result is returned instead.
*
* This utility is helpful for safely handling `Option` values by ensuring you
* always receive a meaningful result, whether or not the `Option` contains a
* value. It is particularly useful for providing default values or alternative
* logic when working with optional values.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(1).pipe(Option.getOrElse(() => 0)))
* // Output: 1
*
* console.log(Option.none().pipe(Option.getOrElse(() => 0)))
* // Output: 0
* ```
*
* @see {@link getOrNull} for a version that returns `null` instead of executing a function.
* @see {@link getOrUndefined} for a version that returns `undefined` instead of executing a function.
*
* @category Getters
* @since 2.0.0
*/
<A, B>(self: Option<A>, onNone: LazyArg<B>): A | B
} = dual(
2,
<A, B>(self: Option<A>, onNone: LazyArg<B>): A | B => isNone(self) ? onNone() : self.value
)
/**
* Returns the provided `Option` `that` if the current `Option` (`self`) is
* `None`; otherwise, it returns `self`.
*
* **Details**
*
* This function provides a fallback mechanism for `Option` values. If the
* current `Option` is `None` (i.e., it contains no value), the `that` function
* is evaluated, and its resulting `Option` is returned. If the current `Option`
* is `Some` (i.e., it contains a value), the original `Option` is returned
* unchanged.
*
* This is particularly useful for chaining fallback values or computations,
* allowing you to provide alternative `Option` values when the first one is
* empty.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
*
* console.log(Option.none().pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
export const orElse: {
/**
* Returns the provided `Option` `that` if the current `Option` (`self`) is
* `None`; otherwise, it returns `self`.
*
* **Details**
*
* This function provides a fallback mechanism for `Option` values. If the
* current `Option` is `None` (i.e., it contains no value), the `that` function
* is evaluated, and its resulting `Option` is returned. If the current `Option`
* is `Some` (i.e., it contains a value), the original `Option` is returned
* unchanged.
*
* This is particularly useful for chaining fallback values or computations,
* allowing you to provide alternative `Option` values when the first one is
* empty.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
*
* console.log(Option.none().pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
<B>(that: LazyArg<Option<B>>): <A>(self: Option<A>) => Option<B | A>
/**
* Returns the provided `Option` `that` if the current `Option` (`self`) is
* `None`; otherwise, it returns `self`.
*
* **Details**
*
* This function provides a fallback mechanism for `Option` values. If the
* current `Option` is `None` (i.e., it contains no value), the `that` function
* is evaluated, and its resulting `Option` is returned. If the current `Option`
* is `Some` (i.e., it contains a value), the original `Option` is returned
* unchanged.
*
* This is particularly useful for chaining fallback values or computations,
* allowing you to provide alternative `Option` values when the first one is
* empty.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.none())))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
*
* console.log(Option.none().pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElse(() => Option.some("b"))))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
<A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B>
} = dual(
2,
<A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B> => isNone(self) ? that() : self
)
/**
* Returns the provided default value wrapped in `Some` if the current `Option`
* (`self`) is `None`; otherwise, returns `self`.
*
* **Details**
*
* This function provides a way to supply a default value for cases where an
* `Option` is `None`. If the current `Option` is empty (`None`), the `onNone`
* function is executed to compute the default value, which is then wrapped in a
* `Some`. If the current `Option` contains a value (`Some`), it is returned as
* is.
*
* This is particularly useful for handling optional values where a fallback
* default needs to be provided explicitly in case of absence.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
export const orElseSome: {
/**
* Returns the provided default value wrapped in `Some` if the current `Option`
* (`self`) is `None`; otherwise, returns `self`.
*
* **Details**
*
* This function provides a way to supply a default value for cases where an
* `Option` is `None`. If the current `Option` is empty (`None`), the `onNone`
* function is executed to compute the default value, which is then wrapped in a
* `Some`. If the current `Option` contains a value (`Some`), it is returned as
* is.
*
* This is particularly useful for handling optional values where a fallback
* default needs to be provided explicitly in case of absence.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
<B>(onNone: LazyArg<B>): <A>(self: Option<A>) => Option<B | A>
/**
* Returns the provided default value wrapped in `Some` if the current `Option`
* (`self`) is `None`; otherwise, returns `self`.
*
* **Details**
*
* This function provides a way to supply a default value for cases where an
* `Option` is `None`. If the current `Option` is empty (`None`), the `onNone`
* function is executed to compute the default value, which is then wrapped in a
* `Some`. If the current `Option` contains a value (`Some`), it is returned as
* is.
*
* This is particularly useful for handling optional values where a fallback
* default needs to be provided explicitly in case of absence.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.none().pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'b' }
*
* console.log(Option.some("a").pipe(Option.orElseSome(() => "b")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Error handling
* @since 2.0.0
*/
<A, B>(self: Option<A>, onNone: LazyArg<B>): Option<A | B>
} = dual(
2,
<A, B>(self: Option<A>, onNone: LazyArg<B>): Option<A | B> => isNone(self) ? some(onNone()) : self
)
/**
* Similar to {@link orElse}, but returns an `Either` wrapped in an `Option` to
* indicate the source of the value.
*
* **Details**
*
* This function allows you to provide a fallback `Option` in case the current
* `Option` (`self`) is `None`. However, unlike `orElse`, it returns the value
* wrapped in an `Either` object, providing additional information about where
* the value came from:
*
* - If the value is from the fallback `Option` (`that`), it is wrapped in an
* `Either.right`.
* - If the value is from the original `Option` (`self`), it is wrapped in an
* `Either.left`.
*
* This is especially useful when you need to differentiate between values
* originating from the primary `Option` and those coming from the fallback,
* while still maintaining the `Option`-style handling.
*
* @category Error handling
* @since 2.0.0
*/
export const orElseEither: {
/**
* Similar to {@link orElse}, but returns an `Either` wrapped in an `Option` to
* indicate the source of the value.
*
* **Details**
*
* This function allows you to provide a fallback `Option` in case the current
* `Option` (`self`) is `None`. However, unlike `orElse`, it returns the value
* wrapped in an `Either` object, providing additional information about where
* the value came from:
*
* - If the value is from the fallback `Option` (`that`), it is wrapped in an
* `Either.right`.
* - If the value is from the original `Option` (`self`), it is wrapped in an
* `Either.left`.
*
* This is especially useful when you need to differentiate between values
* originating from the primary `Option` and those coming from the fallback,
* while still maintaining the `Option`-style handling.
*
* @category Error handling
* @since 2.0.0
*/
<B>(that: LazyArg<Option<B>>): <A>(self: Option<A>) => Option<Either<B, A>>
/**
* Similar to {@link orElse}, but returns an `Either` wrapped in an `Option` to
* indicate the source of the value.
*
* **Details**
*
* This function allows you to provide a fallback `Option` in case the current
* `Option` (`self`) is `None`. However, unlike `orElse`, it returns the value
* wrapped in an `Either` object, providing additional information about where
* the value came from:
*
* - If the value is from the fallback `Option` (`that`), it is wrapped in an
* `Either.right`.
* - If the value is from the original `Option` (`self`), it is wrapped in an
* `Either.left`.
*
* This is especially useful when you need to differentiate between values
* originating from the primary `Option` and those coming from the fallback,
* while still maintaining the `Option`-style handling.
*
* @category Error handling
* @since 2.0.0
*/
<A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<Either<B, A>>
} = dual(
2,
<A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<Either<B, A>> =>
isNone(self) ? map(that(), either.right) : map(self, either.left)
)
/**
* Returns the first `Some` value found in an `Iterable` collection of
* `Option`s, or `None` if no `Some` is found.
*
* **Details**
*
* This function iterates over a collection of `Option` values and returns the
* first `Some` it encounters. If the collection contains only `None` values,
* the result will also be `None`. This utility is useful for efficiently
* finding the first valid value in a sequence of potentially empty or invalid
* options.
*
* The iteration stops as soon as a `Some` is found, making this function
* efficient for large collections.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.firstSomeOf([
* Option.none(),
* Option.some(1),
* Option.some(2)
* ]))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
* ```
*
* @category Error handling
* @since 2.0.0
*/
export const firstSomeOf = <T, C extends Iterable<Option<T>> = Iterable<Option<T>>>(
collection: C
): [C] extends [Iterable<Option<infer A>>] ? Option<A> : never => {
let out: Option<unknown> = none()
for (out of collection) {
if (isSome(out)) {
return out as any
}
}
return out as any
}
/**
* Converts a nullable value into an `Option`. Returns `None` if the value is
* `null` or `undefined`, otherwise wraps the value in a `Some`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.fromNullable(undefined))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.fromNullable(null))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.fromNullable(1))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
* ```
*
* @category Conversions
* @since 2.0.0
*/
export const fromNullable = <A>(
nullableValue: A
): Option<NonNullable<A>> => (nullableValue == null ? none() : some(nullableValue as NonNullable<A>))
/**
* Lifts a function that returns `null` or `undefined` into the `Option`
* context.
*
* **Details**
*
* This function takes a function `f` that might return `null` or `undefined`
* and transforms it into a function that returns an `Option`. The resulting
* function will return:
* - `Some` if the original function produces a non-null, non-undefined value.
* - `None` if the original function produces `null` or `undefined`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const parse = (s: string): number | undefined => {
* const n = parseFloat(s)
* return isNaN(n) ? undefined : n
* }
*
* const parseOption = Option.liftNullable(parse)
*
* console.log(parseOption("1"))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parseOption("not a number"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Conversions
* @since 2.0.0
*/
export const liftNullable = <A extends ReadonlyArray<unknown>, B>(
f: (...a: A) => B | null | undefined
): (...a: A) => Option<NonNullable<B>> =>
(...a) => fromNullable(f(...a))
/**
* Returns the value contained in the `Option` if it is `Some`; otherwise,
* returns `null`.
*
* **Details**
*
* This function provides a way to extract the value of an `Option` while
* falling back to `null` if the `Option` is `None`.
*
* It is particularly useful in scenarios where `null` is an acceptable
* placeholder for the absence of a value, such as when interacting with APIs or
* systems that use `null` as a default for missing values.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.getOrNull(Option.some(1)))
* // Output: 1
*
* console.log(Option.getOrNull(Option.none()))
* // Output: null
* ```
*
* @category Getters
* @since 2.0.0
*/
export const getOrNull: <A>(self: Option<A>) => A | null = getOrElse(constNull)
/**
* Returns the value contained in the `Option` if it is `Some`; otherwise,
* returns `undefined`.
*
* **Details**
*
* This function provides a way to extract the value of an `Option` while
* falling back to `undefined` if the `Option` is `None`.
*
* It is particularly useful in scenarios where `undefined` is an acceptable
* placeholder for the absence of a value, such as when interacting with APIs or
* systems that use `undefined` as a default for missing values.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.getOrUndefined(Option.some(1)))
* // Output: 1
*
* console.log(Option.getOrUndefined(Option.none()))
* // Output: undefined
* ```
*
* @category Getters
* @since 2.0.0
*/
export const getOrUndefined: <A>(self: Option<A>) => A | undefined = getOrElse(constUndefined)
/**
* Lifts a function that throws exceptions into a function that returns an
* `Option`.
*
* **Details**
*
* This utility function takes a function `f` that might throw an exception and
* transforms it into a safer function that returns an `Option`. If the original
* function executes successfully, the result is wrapped in a `Some`. If an
* exception is thrown, the result is `None`, allowing the developer to handle
* errors in a functional, type-safe way.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const parse = Option.liftThrowable(JSON.parse)
*
* console.log(parse("1"))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parse(""))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Conversions
* @since 2.0.0
*/
export const liftThrowable = <A extends ReadonlyArray<unknown>, B>(
f: (...a: A) => B
): (...a: A) => Option<B> =>
(...a) => {
try {
return some(f(...a))
} catch {
return none()
}
}
/**
* Extracts the value of an `Option` or throws an error if the `Option` is
* `None`, using a custom error factory.
*
* **Details**
*
* This function allows you to extract the value of an `Option` when it is
* `Some`. If the `Option` is `None`, it throws an error generated by the
* provided `onNone` function. This utility is particularly useful when you need
* a fail-fast behavior for empty `Option` values and want to provide a custom
* error message or object.
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option } from "effect"
*
* assert.deepStrictEqual(
* Option.getOrThrowWith(Option.some(1), () => new Error('Unexpected None')),
* 1
* )
* assert.throws(() => Option.getOrThrowWith(Option.none(), () => new Error('Unexpected None')))
* ```
*
* @see {@link getOrThrow} for a version that throws a default error.
*
* @category Conversions
* @since 2.0.0
*/
export const getOrThrowWith: {
/**
* Extracts the value of an `Option` or throws an error if the `Option` is
* `None`, using a custom error factory.
*
* **Details**
*
* This function allows you to extract the value of an `Option` when it is
* `Some`. If the `Option` is `None`, it throws an error generated by the
* provided `onNone` function. This utility is particularly useful when you need
* a fail-fast behavior for empty `Option` values and want to provide a custom
* error message or object.
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option } from "effect"
*
* assert.deepStrictEqual(
* Option.getOrThrowWith(Option.some(1), () => new Error('Unexpected None')),
* 1
* )
* assert.throws(() => Option.getOrThrowWith(Option.none(), () => new Error('Unexpected None')))
* ```
*
* @see {@link getOrThrow} for a version that throws a default error.
*
* @category Conversions
* @since 2.0.0
*/
(onNone: () => unknown): <A>(self: Option<A>) => A
/**
* Extracts the value of an `Option` or throws an error if the `Option` is
* `None`, using a custom error factory.
*
* **Details**
*
* This function allows you to extract the value of an `Option` when it is
* `Some`. If the `Option` is `None`, it throws an error generated by the
* provided `onNone` function. This utility is particularly useful when you need
* a fail-fast behavior for empty `Option` values and want to provide a custom
* error message or object.
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option } from "effect"
*
* assert.deepStrictEqual(
* Option.getOrThrowWith(Option.some(1), () => new Error('Unexpected None')),
* 1
* )
* assert.throws(() => Option.getOrThrowWith(Option.none(), () => new Error('Unexpected None')))
* ```
*
* @see {@link getOrThrow} for a version that throws a default error.
*
* @category Conversions
* @since 2.0.0
*/
<A>(self: Option<A>, onNone: () => unknown): A
} = dual(2, <A>(self: Option<A>, onNone: () => unknown): A => {
if (isSome(self)) {
return self.value
}
throw onNone()
})
/**
* Extracts the value of an `Option` or throws a default error if the `Option`
* is `None`.
*
* **Details**
*
* This function extracts the value from an `Option` if it is `Some`. If the
* `Option` is `None`, it throws a default error. It is useful for fail-fast
* scenarios where the absence of a value is treated as an exceptional case and
* a default error is sufficient.
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option } from "effect"
*
* assert.deepStrictEqual(Option.getOrThrow(Option.some(1)), 1)
* assert.throws(() => Option.getOrThrow(Option.none()))
* ```
*
* @see {@link getOrThrowWith} for a version that allows you to provide a custom error.
*
* @category Conversions
* @since 2.0.0
*/
export const getOrThrow: <A>(self: Option<A>) => A = getOrThrowWith(() => new Error("getOrThrow called on a None"))
/**
* Transforms the value inside a `Some` to a new value using the provided
* function, while leaving `None` unchanged.
*
* **Details**
*
* This function applies a mapping function `f` to the value inside an `Option`
* if it is a `Some`. If the `Option` is `None`, it remains unchanged. The
* result is a new `Option` with the transformed value (if it was a `Some`) or
* still `None`.
*
* This utility is particularly useful for chaining transformations in a
* functional way without needing to manually handle `None` cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Mapping over a `Some`
* const someValue = Option.some(2)
*
* console.log(Option.map(someValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'Some', value: 4 }
*
* // Mapping over a `None`
* const noneValue = Option.none<number>()
*
* console.log(Option.map(noneValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
export const map: {
/**
* Transforms the value inside a `Some` to a new value using the provided
* function, while leaving `None` unchanged.
*
* **Details**
*
* This function applies a mapping function `f` to the value inside an `Option`
* if it is a `Some`. If the `Option` is `None`, it remains unchanged. The
* result is a new `Option` with the transformed value (if it was a `Some`) or
* still `None`.
*
* This utility is particularly useful for chaining transformations in a
* functional way without needing to manually handle `None` cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Mapping over a `Some`
* const someValue = Option.some(2)
*
* console.log(Option.map(someValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'Some', value: 4 }
*
* // Mapping over a `None`
* const noneValue = Option.none<number>()
*
* console.log(Option.map(noneValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
<A, B>(f: (a: A) => B): (self: Option<A>) => Option<B>
/**
* Transforms the value inside a `Some` to a new value using the provided
* function, while leaving `None` unchanged.
*
* **Details**
*
* This function applies a mapping function `f` to the value inside an `Option`
* if it is a `Some`. If the `Option` is `None`, it remains unchanged. The
* result is a new `Option` with the transformed value (if it was a `Some`) or
* still `None`.
*
* This utility is particularly useful for chaining transformations in a
* functional way without needing to manually handle `None` cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Mapping over a `Some`
* const someValue = Option.some(2)
*
* console.log(Option.map(someValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'Some', value: 4 }
*
* // Mapping over a `None`
* const noneValue = Option.none<number>()
*
* console.log(Option.map(noneValue, (n) => n * 2))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => B): Option<B>
} = dual(
2,
<A, B>(self: Option<A>, f: (a: A) => B): Option<B> => isNone(self) ? none() : some(f(self.value))
)
/**
* Replaces the value inside a `Some` with the specified constant value, leaving
* `None` unchanged.
*
* **Details**
*
* This function transforms an `Option` by replacing the value inside a `Some`
* with the given constant value `b`. If the `Option` is `None`, it remains
* unchanged.
*
* This is useful when you want to preserve the presence of a value (`Some`) but
* replace its content with a fixed value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Replacing the value of a `Some`
* const someValue = Option.some(42)
*
* console.log(Option.as(someValue, "new value"))
* // Output: { _id: 'Option', _tag: 'Some', value: 'new value' }
*
* // Replacing a `None` (no effect)
* const noneValue = Option.none<number>()
*
* console.log(Option.as(noneValue, "new value"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
export const as: {
/**
* Replaces the value inside a `Some` with the specified constant value, leaving
* `None` unchanged.
*
* **Details**
*
* This function transforms an `Option` by replacing the value inside a `Some`
* with the given constant value `b`. If the `Option` is `None`, it remains
* unchanged.
*
* This is useful when you want to preserve the presence of a value (`Some`) but
* replace its content with a fixed value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Replacing the value of a `Some`
* const someValue = Option.some(42)
*
* console.log(Option.as(someValue, "new value"))
* // Output: { _id: 'Option', _tag: 'Some', value: 'new value' }
*
* // Replacing a `None` (no effect)
* const noneValue = Option.none<number>()
*
* console.log(Option.as(noneValue, "new value"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
<B>(b: B): <X>(self: Option<X>) => Option<B>
/**
* Replaces the value inside a `Some` with the specified constant value, leaving
* `None` unchanged.
*
* **Details**
*
* This function transforms an `Option` by replacing the value inside a `Some`
* with the given constant value `b`. If the `Option` is `None`, it remains
* unchanged.
*
* This is useful when you want to preserve the presence of a value (`Some`) but
* replace its content with a fixed value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Replacing the value of a `Some`
* const someValue = Option.some(42)
*
* console.log(Option.as(someValue, "new value"))
* // Output: { _id: 'Option', _tag: 'Some', value: 'new value' }
*
* // Replacing a `None` (no effect)
* const noneValue = Option.none<number>()
*
* console.log(Option.as(noneValue, "new value"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Mapping
* @since 2.0.0
*/
<X, B>(self: Option<X>, b: B): Option<B>
} = dual(2, <X, B>(self: Option<X>, b: B): Option<B> => map(self, () => b))
/**
* Replaces the value inside a `Some` with the constant value `void`, leaving
* `None` unchanged.
*
* **Details**
*
* This function transforms an `Option` by replacing the value inside a `Some`
* with `void`. If the `Option` is `None`, it remains unchanged.
*
* This is particularly useful in scenarios where the presence or absence of a
* value is significant, but the actual content of the value is irrelevant.
*
* @category Mapping
* @since 2.0.0
*/
export const asVoid: <_>(self: Option<_>) => Option<void> = as(undefined)
const void_: Option<void> = some(undefined)
export {
/**
* @since 2.0.0
*/
void_ as void
}
/**
* Applies a function to the value of a `Some` and flattens the resulting
* `Option`. If the input is `None`, it remains `None`.
*
* **Details**
*
* This function allows you to chain computations that return `Option` values.
* If the input `Option` is `Some`, the provided function `f` is applied to the
* contained value, and the resulting `Option` is returned. If the input is
* `None`, the function is not applied, and the result remains `None`.
*
* This utility is particularly useful for sequencing operations that may fail
* or produce optional results, enabling clean and concise workflows for
* handling such cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Address {
* readonly city: string
* readonly street: Option.Option<string>
* }
*
* interface User {
* readonly id: number
* readonly username: string
* readonly email: Option.Option<string>
* readonly address: Option.Option<Address>
* }
*
* const user: User = {
* id: 1,
* username: "john_doe",
* email: Option.some("john.doe@example.com"),
* address: Option.some({
* city: "New York",
* street: Option.some("123 Main St")
* })
* }
*
* // Use flatMap to extract the street value
* const street = user.address.pipe(
* Option.flatMap((address) => address.street)
* )
*
* console.log(street)
* // Output: { _id: 'Option', _tag: 'Some', value: '123 Main St' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
export const flatMap: {
/**
* Applies a function to the value of a `Some` and flattens the resulting
* `Option`. If the input is `None`, it remains `None`.
*
* **Details**
*
* This function allows you to chain computations that return `Option` values.
* If the input `Option` is `Some`, the provided function `f` is applied to the
* contained value, and the resulting `Option` is returned. If the input is
* `None`, the function is not applied, and the result remains `None`.
*
* This utility is particularly useful for sequencing operations that may fail
* or produce optional results, enabling clean and concise workflows for
* handling such cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Address {
* readonly city: string
* readonly street: Option.Option<string>
* }
*
* interface User {
* readonly id: number
* readonly username: string
* readonly email: Option.Option<string>
* readonly address: Option.Option<Address>
* }
*
* const user: User = {
* id: 1,
* username: "john_doe",
* email: Option.some("john.doe@example.com"),
* address: Option.some({
* city: "New York",
* street: Option.some("123 Main St")
* })
* }
*
* // Use flatMap to extract the street value
* const street = user.address.pipe(
* Option.flatMap((address) => address.street)
* )
*
* console.log(street)
* // Output: { _id: 'Option', _tag: 'Some', value: '123 Main St' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(f: (a: A) => Option<B>): (self: Option<A>) => Option<B>
/**
* Applies a function to the value of a `Some` and flattens the resulting
* `Option`. If the input is `None`, it remains `None`.
*
* **Details**
*
* This function allows you to chain computations that return `Option` values.
* If the input `Option` is `Some`, the provided function `f` is applied to the
* contained value, and the resulting `Option` is returned. If the input is
* `None`, the function is not applied, and the result remains `None`.
*
* This utility is particularly useful for sequencing operations that may fail
* or produce optional results, enabling clean and concise workflows for
* handling such cases.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Address {
* readonly city: string
* readonly street: Option.Option<string>
* }
*
* interface User {
* readonly id: number
* readonly username: string
* readonly email: Option.Option<string>
* readonly address: Option.Option<Address>
* }
*
* const user: User = {
* id: 1,
* username: "john_doe",
* email: Option.some("john.doe@example.com"),
* address: Option.some({
* city: "New York",
* street: Option.some("123 Main St")
* })
* }
*
* // Use flatMap to extract the street value
* const street = user.address.pipe(
* Option.flatMap((address) => address.street)
* )
*
* console.log(street)
* // Output: { _id: 'Option', _tag: 'Some', value: '123 Main St' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => Option<B>): Option<B>
} = dual(
2,
<A, B>(self: Option<A>, f: (a: A) => Option<B>): Option<B> => isNone(self) ? none() : f(self.value)
)
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
export const andThen: {
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(f: (a: A) => Option<B>): (self: Option<A>) => Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<B>(f: Option<B>): <A>(self: Option<A>) => Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(f: (a: A) => B): (self: Option<A>) => Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<B>(f: NotFunction<B>): <A>(self: Option<A>) => Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => Option<B>): Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: Option<B>): Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => B): Option<B>
/**
* Chains two `Option`s together. The second `Option` can either be a static
* value or depend on the result of the first `Option`.
*
* **Details**
*
* This function enables sequencing of two `Option` computations. If the first
* `Option` is `Some`, the second `Option` is evaluated. The second `Option` can
* either:
*
* - Be a static `Option` value.
* - Be a function that produces an `Option`, optionally based on the value of
* the first `Option`.
*
* If the first `Option` is `None`, the function skips the evaluation of the
* second `Option` and directly returns `None`.
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: NotFunction<B>): Option<B>
} = dual(
2,
<A, B>(self: Option<A>, f: (a: A) => Option<B> | Option<B>): Option<B> =>
flatMap(self, (a) => {
const b = isFunction(f) ? f(a) : f
return isOption(b) ? b : some(b)
})
)
/**
* Combines `flatMap` and `fromNullable`, transforming the value inside a `Some`
* using a function that may return `null` or `undefined`.
*
* **Details**
*
* This function applies a transformation function `f` to the value inside a
* `Some`. The function `f` may return a value, `null`, or `undefined`. If `f`
* returns a value, it is wrapped in a `Some`. If `f` returns `null` or
* `undefined`, the result is `None`. If the input `Option` is `None`, the
* function is not applied, and `None` is returned.
*
* This utility is particularly useful when working with deeply nested optional
* values or chaining computations that may result in `null` or `undefined` at
* some point.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Employee {
* company?: {
* address?: {
* street?: {
* name?: string
* }
* }
* }
* }
*
* const employee1: Employee = { company: { address: { street: { name: "high street" } } } }
*
* // Extracting a deeply nested property
* console.log(
* Option.some(employee1)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'Some', value: 'high street' }
*
* const employee2: Employee = { company: { address: { street: {} } } }
*
* // Property does not exist
* console.log(
* Option.some(employee2)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
export const flatMapNullable: {
/**
* Combines `flatMap` and `fromNullable`, transforming the value inside a `Some`
* using a function that may return `null` or `undefined`.
*
* **Details**
*
* This function applies a transformation function `f` to the value inside a
* `Some`. The function `f` may return a value, `null`, or `undefined`. If `f`
* returns a value, it is wrapped in a `Some`. If `f` returns `null` or
* `undefined`, the result is `None`. If the input `Option` is `None`, the
* function is not applied, and `None` is returned.
*
* This utility is particularly useful when working with deeply nested optional
* values or chaining computations that may result in `null` or `undefined` at
* some point.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Employee {
* company?: {
* address?: {
* street?: {
* name?: string
* }
* }
* }
* }
*
* const employee1: Employee = { company: { address: { street: { name: "high street" } } } }
*
* // Extracting a deeply nested property
* console.log(
* Option.some(employee1)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'Some', value: 'high street' }
*
* const employee2: Employee = { company: { address: { street: {} } } }
*
* // Property does not exist
* console.log(
* Option.some(employee2)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(f: (a: A) => B | null | undefined): (self: Option<A>) => Option<NonNullable<B>>
/**
* Combines `flatMap` and `fromNullable`, transforming the value inside a `Some`
* using a function that may return `null` or `undefined`.
*
* **Details**
*
* This function applies a transformation function `f` to the value inside a
* `Some`. The function `f` may return a value, `null`, or `undefined`. If `f`
* returns a value, it is wrapped in a `Some`. If `f` returns `null` or
* `undefined`, the result is `None`. If the input `Option` is `None`, the
* function is not applied, and `None` is returned.
*
* This utility is particularly useful when working with deeply nested optional
* values or chaining computations that may result in `null` or `undefined` at
* some point.
*
* @example
* ```ts
* import { Option } from "effect"
*
* interface Employee {
* company?: {
* address?: {
* street?: {
* name?: string
* }
* }
* }
* }
*
* const employee1: Employee = { company: { address: { street: { name: "high street" } } } }
*
* // Extracting a deeply nested property
* console.log(
* Option.some(employee1)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'Some', value: 'high street' }
*
* const employee2: Employee = { company: { address: { street: {} } } }
*
* // Property does not exist
* console.log(
* Option.some(employee2)
* .pipe(Option.flatMapNullable((employee) => employee.company?.address?.street?.name))
* )
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => B | null | undefined): Option<NonNullable<B>>
} = dual(
2,
<A, B>(self: Option<A>, f: (a: A) => B | null | undefined): Option<NonNullable<B>> =>
isNone(self) ? none() : fromNullable(f(self.value))
)
/**
* Flattens an `Option` of `Option` into a single `Option`.
*
* **Details**
*
* This function takes an `Option` that wraps another `Option` and flattens it
* into a single `Option`. If the outer `Option` is `Some`, the function
* extracts the inner `Option`. If the outer `Option` is `None`, the result
* remains `None`.
*
* This is useful for simplifying nested `Option` structures that may arise
* during functional operations.
*
* @category Sequencing
* @since 2.0.0
*/
export const flatten: <A>(self: Option<Option<A>>) => Option<A> = flatMap(identity)
/**
* Combines two `Option`s, keeping the value from the second `Option` if both
* are `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the second one if the first is
* `Some`. If the first `Option` is `None`, the result will also be `None`,
* regardless of the second `Option`. It effectively "zips" the two `Option`s
* while discarding the value from the first `Option`.
*
* This is particularly useful when sequencing computations where the result of
* the first computation is not needed, and you only care about the result of
* the second computation.
*
* @category Zipping
* @since 2.0.0
*/
export const zipRight: {
/**
* Combines two `Option`s, keeping the value from the second `Option` if both
* are `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the second one if the first is
* `Some`. If the first `Option` is `None`, the result will also be `None`,
* regardless of the second `Option`. It effectively "zips" the two `Option`s
* while discarding the value from the first `Option`.
*
* This is particularly useful when sequencing computations where the result of
* the first computation is not needed, and you only care about the result of
* the second computation.
*
* @category Zipping
* @since 2.0.0
*/
<B>(that: Option<B>): <_>(self: Option<_>) => Option<B>
/**
* Combines two `Option`s, keeping the value from the second `Option` if both
* are `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the second one if the first is
* `Some`. If the first `Option` is `None`, the result will also be `None`,
* regardless of the second `Option`. It effectively "zips" the two `Option`s
* while discarding the value from the first `Option`.
*
* This is particularly useful when sequencing computations where the result of
* the first computation is not needed, and you only care about the result of
* the second computation.
*
* @category Zipping
* @since 2.0.0
*/
<X, B>(self: Option<X>, that: Option<B>): Option<B>
} = dual(2, <X, B>(self: Option<X>, that: Option<B>): Option<B> => flatMap(self, () => that))
/**
* Combines two `Option`s, keeping the value from the first `Option` if both are
* `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the first one if it is `Some`.
* If either the first `Option` or the second `Option` is `None`, the result
* will be `None`. This operation "zips" the two `Option`s while discarding the
* value from the second `Option`.
*
* This is useful when sequencing computations where the second `Option`
* represents a dependency or condition that must hold, but its value is
* irrelevant.
*
* @category Zipping
* @since 2.0.0
*/
export const zipLeft: {
/**
* Combines two `Option`s, keeping the value from the first `Option` if both are
* `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the first one if it is `Some`.
* If either the first `Option` or the second `Option` is `None`, the result
* will be `None`. This operation "zips" the two `Option`s while discarding the
* value from the second `Option`.
*
* This is useful when sequencing computations where the second `Option`
* represents a dependency or condition that must hold, but its value is
* irrelevant.
*
* @category Zipping
* @since 2.0.0
*/
<_>(that: Option<_>): <A>(self: Option<A>) => Option<A>
/**
* Combines two `Option`s, keeping the value from the first `Option` if both are
* `Some`.
*
* **Details**
*
* This function takes two `Option`s and returns the first one if it is `Some`.
* If either the first `Option` or the second `Option` is `None`, the result
* will be `None`. This operation "zips" the two `Option`s while discarding the
* value from the second `Option`.
*
* This is useful when sequencing computations where the second `Option`
* represents a dependency or condition that must hold, but its value is
* irrelevant.
*
* @category Zipping
* @since 2.0.0
*/
<A, X>(self: Option<A>, that: Option<X>): Option<A>
} = dual(2, <A, X>(self: Option<A>, that: Option<X>): Option<A> => tap(self, () => that))
/**
* Composes two functions that return `Option` values, creating a new function
* that chains them together.
*
* **Details**
*
* This function allows you to compose two computations, each represented by a
* function that returns an `Option`. The result of the first function is passed
* to the second function if it is `Some`. If the first function returns `None`,
* the composed function short-circuits and returns `None` without invoking the
* second function.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const parse = (s: string): Option.Option<number> => isNaN(Number(s)) ? Option.none() : Option.some(Number(s))
*
* const double = (n: number): Option.Option<number> => n > 0 ? Option.some(n * 2) : Option.none()
*
* const parseAndDouble = Option.composeK(parse, double)
*
* console.log(parseAndDouble("42"))
* // Output: { _id: 'Option', _tag: 'Some', value: 84 }
*
* console.log(parseAndDouble("not a number"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
export const composeK: {
/**
* Composes two functions that return `Option` values, creating a new function
* that chains them together.
*
* **Details**
*
* This function allows you to compose two computations, each represented by a
* function that returns an `Option`. The result of the first function is passed
* to the second function if it is `Some`. If the first function returns `None`,
* the composed function short-circuits and returns `None` without invoking the
* second function.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const parse = (s: string): Option.Option<number> => isNaN(Number(s)) ? Option.none() : Option.some(Number(s))
*
* const double = (n: number): Option.Option<number> => n > 0 ? Option.some(n * 2) : Option.none()
*
* const parseAndDouble = Option.composeK(parse, double)
*
* console.log(parseAndDouble("42"))
* // Output: { _id: 'Option', _tag: 'Some', value: 84 }
*
* console.log(parseAndDouble("not a number"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<B, C>(bfc: (b: B) => Option<C>): <A>(afb: (a: A) => Option<B>) => (a: A) => Option<C>
/**
* Composes two functions that return `Option` values, creating a new function
* that chains them together.
*
* **Details**
*
* This function allows you to compose two computations, each represented by a
* function that returns an `Option`. The result of the first function is passed
* to the second function if it is `Some`. If the first function returns `None`,
* the composed function short-circuits and returns `None` without invoking the
* second function.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const parse = (s: string): Option.Option<number> => isNaN(Number(s)) ? Option.none() : Option.some(Number(s))
*
* const double = (n: number): Option.Option<number> => n > 0 ? Option.some(n * 2) : Option.none()
*
* const parseAndDouble = Option.composeK(parse, double)
*
* console.log(parseAndDouble("42"))
* // Output: { _id: 'Option', _tag: 'Some', value: 84 }
*
* console.log(parseAndDouble("not a number"))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, B, C>(afb: (a: A) => Option<B>, bfc: (b: B) => Option<C>): (a: A) => Option<C>
} = dual(2, <A, B, C>(afb: (a: A) => Option<B>, bfc: (b: B) => Option<C>) => (a: A): Option<C> => flatMap(afb(a), bfc))
/**
* Applies the provided function `f` to the value of the `Option` if it is
* `Some` and returns the original `Option`, unless `f` returns `None`, in which
* case it returns `None`.
*
* **Details**
*
* This function allows you to perform additional computations on the value of
* an `Option` without modifying its original value. If the `Option` is `Some`,
* the provided function `f` is executed with the value, and its result
* determines whether the original `Option` is returned (`Some`) or the result
* is `None` if `f` returns `None`. If the input `Option` is `None`, the
* function is not executed, and `None` is returned.
*
* This is particularly useful for applying side conditions or performing
* validation checks while retaining the original `Option`'s value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const getInteger = (n: number) => Number.isInteger(n) ? Option.some(n) : Option.none()
*
* console.log(Option.tap(Option.none(), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.tap(Option.some(1), getInteger))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(Option.tap(Option.some(1.14), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
export const tap: {
/**
* Applies the provided function `f` to the value of the `Option` if it is
* `Some` and returns the original `Option`, unless `f` returns `None`, in which
* case it returns `None`.
*
* **Details**
*
* This function allows you to perform additional computations on the value of
* an `Option` without modifying its original value. If the `Option` is `Some`,
* the provided function `f` is executed with the value, and its result
* determines whether the original `Option` is returned (`Some`) or the result
* is `None` if `f` returns `None`. If the input `Option` is `None`, the
* function is not executed, and `None` is returned.
*
* This is particularly useful for applying side conditions or performing
* validation checks while retaining the original `Option`'s value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const getInteger = (n: number) => Number.isInteger(n) ? Option.some(n) : Option.none()
*
* console.log(Option.tap(Option.none(), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.tap(Option.some(1), getInteger))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(Option.tap(Option.some(1.14), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, X>(f: (a: A) => Option<X>): (self: Option<A>) => Option<A>
/**
* Applies the provided function `f` to the value of the `Option` if it is
* `Some` and returns the original `Option`, unless `f` returns `None`, in which
* case it returns `None`.
*
* **Details**
*
* This function allows you to perform additional computations on the value of
* an `Option` without modifying its original value. If the `Option` is `Some`,
* the provided function `f` is executed with the value, and its result
* determines whether the original `Option` is returned (`Some`) or the result
* is `None` if `f` returns `None`. If the input `Option` is `None`, the
* function is not executed, and `None` is returned.
*
* This is particularly useful for applying side conditions or performing
* validation checks while retaining the original `Option`'s value.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const getInteger = (n: number) => Number.isInteger(n) ? Option.some(n) : Option.none()
*
* console.log(Option.tap(Option.none(), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(Option.tap(Option.some(1), getInteger))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(Option.tap(Option.some(1.14), getInteger))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Sequencing
* @since 2.0.0
*/
<A, X>(self: Option<A>, f: (a: A) => Option<X>): Option<A>
} = dual(2, <A, X>(self: Option<A>, f: (a: A) => Option<X>): Option<A> => flatMap(self, (a) => map(f(a), () => a)))
/**
* Combines two `Option` values into a single `Option` containing a tuple of
* their values if both are `Some`.
*
* **Details**
*
* This function takes two `Option`s and combines their values into a tuple `[A,
* B]` if both are `Some`. If either of the `Option`s is `None`, the result is
* `None`. This is particularly useful for combining multiple `Option` values
* into a single one, ensuring both contain valid values.
*
* @category Combining
* @since 2.0.0
*/
export const product = <A, B>(self: Option<A>, that: Option<B>): Option<[A, B]> =>
isSome(self) && isSome(that) ? some([self.value, that.value]) : none()
/**
* Combines an `Option` with a collection of `Option`s into a single `Option`
* containing a tuple of their values if all are `Some`.
*
* **Details**
*
* This function takes a primary `Option` and a collection of `Option`s and
* combines their values into a tuple `[A, ...Array<A>]` if all are `Some`. If
* the primary `Option` or any `Option` in the collection is `None`, the result
* is `None`.
*
* @category Combining
* @since 2.0.0
*/
export const productMany = <A>(
self: Option<A>,
collection: Iterable<Option<A>>
): Option<[A, ...Array<A>]> => {
if (isNone(self)) {
return none()
}
const out: [A, ...Array<A>] = [self.value]
for (const o of collection) {
if (isNone(o)) {
return none()
}
out.push(o.value)
}
return some(out)
}
/**
* Combines a structure of `Option`s into a single `Option` containing the
* values with the same structure.
*
* **Details**
*
* This function takes a structure of `Option`s (a tuple, struct, or iterable)
* and produces a single `Option` that contains the values from the input
* structure if all `Option`s are `Some`. If any `Option` in the input is
* `None`, the result is `None`. The structure of the input is preserved in the
* output.
*
* - If the input is a tuple (e.g., an array), the result will be an `Option`
* containing a tuple with the same length.
* - If the input is a struct (e.g., an object), the result will be an `Option`
* containing a struct with the same keys.
* - If the input is an iterable, the result will be an `Option` containing an
* array.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const maybeName: Option.Option<string> = Option.some("John")
* const maybeAge: Option.Option<number> = Option.some(25)
*
* // ┌─── Option<[string, number]>
* // ▼
* const tuple = Option.all([maybeName, maybeAge])
* console.log(tuple)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: [ 'John', 25 ] }
*
* // ┌─── Option<{ name: string; age: number; }>
* // ▼
* const struct = Option.all({ name: maybeName, age: maybeAge })
* console.log(struct)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: { name: 'John', age: 25 } }
* ```
*
* @category Combining
* @since 2.0.0
*/
// @ts-expect-error
export const all: <const I extends Iterable<Option<any>> | Record<string, Option<any>>>(
input: I
) => [I] extends [ReadonlyArray<Option<any>>] ? Option<
{ -readonly [K in keyof I]: [I[K]] extends [Option<infer A>] ? A : never }
>
: [I] extends [Iterable<Option<infer A>>] ? Option<Array<A>>
: Option<{ -readonly [K in keyof I]: [I[K]] extends [Option<infer A>] ? A : never }> = (
input: Iterable<Option<any>> | Record<string, Option<any>>
): Option<any> => {
if (Symbol.iterator in input) {
const out: Array<Option<any>> = []
for (const o of (input as Iterable<Option<any>>)) {
if (isNone(o)) {
return none()
}
out.push(o.value)
}
return some(out)
}
const out: Record<string, any> = {}
for (const key of Object.keys(input)) {
const o = input[key]
if (isNone(o)) {
return none()
}
out[key] = o.value
}
return some(out)
}
/**
* Combines two `Option` values into a new `Option` by applying a provided
* function to their values.
*
* **Details**
*
* This function takes two `Option` values (`self` and `that`) and a combining
* function `f`. If both `Option` values are `Some`, the function `f` is applied
* to their values, and the result is wrapped in a new `Some`. If either
* `Option` is `None`, the result is `None`.
*
* This utility is useful for combining two optional computations into a single
* result while maintaining type safety and avoiding explicit checks for `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const maybeName: Option.Option<string> = Option.some("John")
* const maybeAge: Option.Option<number> = Option.some(25)
*
* // Combine the name and age into a person object
* const person = Option.zipWith(maybeName, maybeAge, (name, age) => ({
* name: name.toUpperCase(),
* age
* }))
*
* console.log(person)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: { name: 'JOHN', age: 25 } }
* ```
*
* @category Zipping
* @since 2.0.0
*/
export const zipWith: {
/**
* Combines two `Option` values into a new `Option` by applying a provided
* function to their values.
*
* **Details**
*
* This function takes two `Option` values (`self` and `that`) and a combining
* function `f`. If both `Option` values are `Some`, the function `f` is applied
* to their values, and the result is wrapped in a new `Some`. If either
* `Option` is `None`, the result is `None`.
*
* This utility is useful for combining two optional computations into a single
* result while maintaining type safety and avoiding explicit checks for `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const maybeName: Option.Option<string> = Option.some("John")
* const maybeAge: Option.Option<number> = Option.some(25)
*
* // Combine the name and age into a person object
* const person = Option.zipWith(maybeName, maybeAge, (name, age) => ({
* name: name.toUpperCase(),
* age
* }))
*
* console.log(person)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: { name: 'JOHN', age: 25 } }
* ```
*
* @category Zipping
* @since 2.0.0
*/
<B, A, C>(that: Option<B>, f: (a: A, b: B) => C): (self: Option<A>) => Option<C>
/**
* Combines two `Option` values into a new `Option` by applying a provided
* function to their values.
*
* **Details**
*
* This function takes two `Option` values (`self` and `that`) and a combining
* function `f`. If both `Option` values are `Some`, the function `f` is applied
* to their values, and the result is wrapped in a new `Some`. If either
* `Option` is `None`, the result is `None`.
*
* This utility is useful for combining two optional computations into a single
* result while maintaining type safety and avoiding explicit checks for `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const maybeName: Option.Option<string> = Option.some("John")
* const maybeAge: Option.Option<number> = Option.some(25)
*
* // Combine the name and age into a person object
* const person = Option.zipWith(maybeName, maybeAge, (name, age) => ({
* name: name.toUpperCase(),
* age
* }))
*
* console.log(person)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: { name: 'JOHN', age: 25 } }
* ```
*
* @category Zipping
* @since 2.0.0
*/
<A, B, C>(self: Option<A>, that: Option<B>, f: (a: A, b: B) => C): Option<C>
} = dual(
3,
<A, B, C>(self: Option<A>, that: Option<B>, f: (a: A, b: B) => C): Option<C> =>
map(product(self, that), ([a, b]) => f(a, b))
)
/**
* Applies a function inside a `Some` to a value inside another `Some`,
* combining them into a new `Option`.
*
* **Details**
*
* This function allows you to apply a function wrapped in an `Option` (`self`)
* to a value wrapped in another `Option` (`that`). If both `Option`s are
* `Some`, the function is applied to the value, and the result is wrapped in a
* new `Some`. If either `Option` is `None`, the result is `None`.
*
* @category Combining
* @since 2.0.0
*/
export const ap: {
/**
* Applies a function inside a `Some` to a value inside another `Some`,
* combining them into a new `Option`.
*
* **Details**
*
* This function allows you to apply a function wrapped in an `Option` (`self`)
* to a value wrapped in another `Option` (`that`). If both `Option`s are
* `Some`, the function is applied to the value, and the result is wrapped in a
* new `Some`. If either `Option` is `None`, the result is `None`.
*
* @category Combining
* @since 2.0.0
*/
<A>(that: Option<A>): <B>(self: Option<(a: A) => B>) => Option<B>
/**
* Applies a function inside a `Some` to a value inside another `Some`,
* combining them into a new `Option`.
*
* **Details**
*
* This function allows you to apply a function wrapped in an `Option` (`self`)
* to a value wrapped in another `Option` (`that`). If both `Option`s are
* `Some`, the function is applied to the value, and the result is wrapped in a
* new `Some`. If either `Option` is `None`, the result is `None`.
*
* @category Combining
* @since 2.0.0
*/
<A, B>(self: Option<(a: A) => B>, that: Option<A>): Option<B>
} = dual(2, <A, B>(self: Option<(a: A) => B>, that: Option<A>): Option<B> => zipWith(self, that, (f, a) => f(a)))
/**
* Reduces an `Iterable` of `Option<A>` to a single value of type `B`, ignoring
* elements that are `None`.
*
* **Details**
*
* This function takes an initial value of type `B` and a reducing function `f`
* that combines the accumulator with values of type `A`. It processes an
* iterable of `Option<A>`, applying `f` only to the `Some` values while
* ignoring the `None` values. The result is a single value of type `B`.
*
* This utility is particularly useful for aggregating values from an iterable
* of `Option`s while skipping the absent (`None`) values.
*
* @example
* ```ts
* import { Option, pipe } from "effect"
*
* const iterable = [Option.some(1), Option.none(), Option.some(2), Option.none()]
*
* console.log(pipe(iterable, Option.reduceCompact(0, (b, a) => b + a)))
* // Output: 3
* ```
*
* @category Reducing
* @since 2.0.0
*/
export const reduceCompact: {
/**
* Reduces an `Iterable` of `Option<A>` to a single value of type `B`, ignoring
* elements that are `None`.
*
* **Details**
*
* This function takes an initial value of type `B` and a reducing function `f`
* that combines the accumulator with values of type `A`. It processes an
* iterable of `Option<A>`, applying `f` only to the `Some` values while
* ignoring the `None` values. The result is a single value of type `B`.
*
* This utility is particularly useful for aggregating values from an iterable
* of `Option`s while skipping the absent (`None`) values.
*
* @example
* ```ts
* import { Option, pipe } from "effect"
*
* const iterable = [Option.some(1), Option.none(), Option.some(2), Option.none()]
*
* console.log(pipe(iterable, Option.reduceCompact(0, (b, a) => b + a)))
* // Output: 3
* ```
*
* @category Reducing
* @since 2.0.0
*/
<B, A>(b: B, f: (b: B, a: A) => B): (self: Iterable<Option<A>>) => B
/**
* Reduces an `Iterable` of `Option<A>` to a single value of type `B`, ignoring
* elements that are `None`.
*
* **Details**
*
* This function takes an initial value of type `B` and a reducing function `f`
* that combines the accumulator with values of type `A`. It processes an
* iterable of `Option<A>`, applying `f` only to the `Some` values while
* ignoring the `None` values. The result is a single value of type `B`.
*
* This utility is particularly useful for aggregating values from an iterable
* of `Option`s while skipping the absent (`None`) values.
*
* @example
* ```ts
* import { Option, pipe } from "effect"
*
* const iterable = [Option.some(1), Option.none(), Option.some(2), Option.none()]
*
* console.log(pipe(iterable, Option.reduceCompact(0, (b, a) => b + a)))
* // Output: 3
* ```
*
* @category Reducing
* @since 2.0.0
*/
<A, B>(self: Iterable<Option<A>>, b: B, f: (b: B, a: A) => B): B
} = dual(
3,
<A, B>(self: Iterable<Option<A>>, b: B, f: (b: B, a: A) => B): B => {
let out: B = b
for (const oa of self) {
if (isSome(oa)) {
out = f(out, oa.value)
}
}
return out
}
)
/**
* Converts an `Option` into an `Array`.
* If the input is `None`, an empty array is returned.
* If the input is `Some`, its value is wrapped in a single-element array.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.toArray(Option.some(1)))
* // Output: [1]
*
* console.log(Option.toArray(Option.none()))
* // Output: []
* ```
*
* @category Conversions
* @since 2.0.0
*/
export const toArray = <A>(self: Option<A>): Array<A> => isNone(self) ? [] : [self.value]
/**
* Splits an `Option` into two `Option`s based on the result of a mapping
* function that produces an `Either`.
*
* **Details**
*
* This function takes an `Option` and a mapping function `f` that converts its
* value into an `Either`. It returns a tuple of two `Option`s:
*
* - The first `Option` (`left`) contains the value from the `Left` side of the
* `Either` if it exists, otherwise `None`.
* - The second `Option` (`right`) contains the value from the `Right` side of
* the `Either` if it exists, otherwise `None`.
*
* If the input `Option` is `None`, both returned `Option`s are `None`.
*
* This utility is useful for filtering and categorizing the contents of an
* `Option` based on a bifurcating computation.
*
* @category Filtering
* @since 2.0.0
*/
export const partitionMap: {
/**
* Splits an `Option` into two `Option`s based on the result of a mapping
* function that produces an `Either`.
*
* **Details**
*
* This function takes an `Option` and a mapping function `f` that converts its
* value into an `Either`. It returns a tuple of two `Option`s:
*
* - The first `Option` (`left`) contains the value from the `Left` side of the
* `Either` if it exists, otherwise `None`.
* - The second `Option` (`right`) contains the value from the `Right` side of
* the `Either` if it exists, otherwise `None`.
*
* If the input `Option` is `None`, both returned `Option`s are `None`.
*
* This utility is useful for filtering and categorizing the contents of an
* `Option` based on a bifurcating computation.
*
* @category Filtering
* @since 2.0.0
*/
<A, B, C>(f: (a: A) => Either<C, B>): (self: Option<A>) => [left: Option<B>, right: Option<C>]
/**
* Splits an `Option` into two `Option`s based on the result of a mapping
* function that produces an `Either`.
*
* **Details**
*
* This function takes an `Option` and a mapping function `f` that converts its
* value into an `Either`. It returns a tuple of two `Option`s:
*
* - The first `Option` (`left`) contains the value from the `Left` side of the
* `Either` if it exists, otherwise `None`.
* - The second `Option` (`right`) contains the value from the `Right` side of
* the `Either` if it exists, otherwise `None`.
*
* If the input `Option` is `None`, both returned `Option`s are `None`.
*
* This utility is useful for filtering and categorizing the contents of an
* `Option` based on a bifurcating computation.
*
* @category Filtering
* @since 2.0.0
*/
<A, B, C>(self: Option<A>, f: (a: A) => Either<C, B>): [left: Option<B>, right: Option<C>]
} = dual(2, <A, B, C>(
self: Option<A>,
f: (a: A) => Either<C, B>
): [excluded: Option<B>, satisfying: Option<C>] => {
if (isNone(self)) {
return [none(), none()]
}
const e = f(self.value)
return either.isLeft(e) ? [some(e.left), none()] : [none(), some(e.right)]
})
// TODO(4.0): remove?
/**
* Alias of {@link flatMap}.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Transform and filter numbers
* const transformEven = (n: Option.Option<number>): Option.Option<string> =>
* Option.filterMap(n, (n) => (n % 2 === 0 ? Option.some(`Even: ${n}`) : Option.none()))
*
* console.log(transformEven(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(1)))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(2)))
* // Output: { _id: 'Option', _tag: 'Some', value: 'Even: 2' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
export const filterMap: {
// TODO(4.0): remove?
/**
* Alias of {@link flatMap}.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Transform and filter numbers
* const transformEven = (n: Option.Option<number>): Option.Option<string> =>
* Option.filterMap(n, (n) => (n % 2 === 0 ? Option.some(`Even: ${n}`) : Option.none()))
*
* console.log(transformEven(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(1)))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(2)))
* // Output: { _id: 'Option', _tag: 'Some', value: 'Even: 2' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A, B>(f: (a: A) => Option<B>): (self: Option<A>) => Option<B>
// TODO(4.0): remove?
/**
* Alias of {@link flatMap}.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Transform and filter numbers
* const transformEven = (n: Option.Option<number>): Option.Option<string> =>
* Option.filterMap(n, (n) => (n % 2 === 0 ? Option.some(`Even: ${n}`) : Option.none()))
*
* console.log(transformEven(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(1)))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(transformEven(Option.some(2)))
* // Output: { _id: 'Option', _tag: 'Some', value: 'Even: 2' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A, B>(self: Option<A>, f: (a: A) => Option<B>): Option<B>
} = flatMap
/**
* Filters an `Option` using a predicate. If the predicate is not satisfied or the `Option` is `None` returns `None`.
*
* If you need to change the type of the `Option` in addition to filtering, see `filterMap`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const removeEmptyString = (input: Option.Option<string>) =>
* Option.filter(input, (value) => value !== "")
*
* console.log(removeEmptyString(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("a")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
export const filter: {
/**
* Filters an `Option` using a predicate. If the predicate is not satisfied or the `Option` is `None` returns `None`.
*
* If you need to change the type of the `Option` in addition to filtering, see `filterMap`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const removeEmptyString = (input: Option.Option<string>) =>
* Option.filter(input, (value) => value !== "")
*
* console.log(removeEmptyString(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("a")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A, B extends A>(refinement: Refinement<NoInfer<A>, B>): (self: Option<A>) => Option<B>
/**
* Filters an `Option` using a predicate. If the predicate is not satisfied or the `Option` is `None` returns `None`.
*
* If you need to change the type of the `Option` in addition to filtering, see `filterMap`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const removeEmptyString = (input: Option.Option<string>) =>
* Option.filter(input, (value) => value !== "")
*
* console.log(removeEmptyString(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("a")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A>(predicate: Predicate<NoInfer<A>>): (self: Option<A>) => Option<A>
/**
* Filters an `Option` using a predicate. If the predicate is not satisfied or the `Option` is `None` returns `None`.
*
* If you need to change the type of the `Option` in addition to filtering, see `filterMap`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const removeEmptyString = (input: Option.Option<string>) =>
* Option.filter(input, (value) => value !== "")
*
* console.log(removeEmptyString(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("a")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A, B extends A>(self: Option<A>, refinement: Refinement<A, B>): Option<B>
/**
* Filters an `Option` using a predicate. If the predicate is not satisfied or the `Option` is `None` returns `None`.
*
* If you need to change the type of the `Option` in addition to filtering, see `filterMap`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const removeEmptyString = (input: Option.Option<string>) =>
* Option.filter(input, (value) => value !== "")
*
* console.log(removeEmptyString(Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("")))
* // Output: { _id: 'Option', _tag: 'None' }
*
* console.log(removeEmptyString(Option.some("a")))
* // Output: { _id: 'Option', _tag: 'Some', value: 'a' }
* ```
*
* @category Filtering
* @since 2.0.0
*/
<A>(self: Option<A>, predicate: Predicate<A>): Option<A>
} = dual(
2,
<A>(self: Option<A>, predicate: Predicate<A>): Option<A> =>
filterMap(self, (b) => (predicate(b) ? option.some(b) : option.none))
)
/**
* Creates an `Equivalence` instance for comparing `Option` values, using a
* provided `Equivalence` for the inner type.
*
* **Details**
*
* This function takes an `Equivalence` instance for a specific type `A` and
* produces an `Equivalence` instance for `Option<A>`. The resulting
* `Equivalence` determines whether two `Option` values are equivalent:
*
* - Two `None`s are considered equivalent.
* - A `Some` and a `None` are not equivalent.
* - Two `Some` values are equivalent if their inner values are equivalent
* according to the provided `Equivalence`.
*
* **Example** (Comparing Optional Numbers for Equivalence)
*
* ```ts
* import { Number, Option } from "effect"
*
* const isEquivalent = Option.getEquivalence(Number.Equivalence)
*
* console.log(isEquivalent(Option.none(), Option.none()))
* // Output: true
*
* console.log(isEquivalent(Option.none(), Option.some(1)))
* // Output: false
*
* console.log(isEquivalent(Option.some(1), Option.none()))
* // Output: false
*
* console.log(isEquivalent(Option.some(1), Option.some(2)))
* // Output: false
*
* console.log(isEquivalent(Option.some(1), Option.some(1)))
* // Output: true
* ```
*
* @category Equivalence
* @since 2.0.0
*/
export const getEquivalence = <A>(isEquivalent: Equivalence.Equivalence<A>): Equivalence.Equivalence<Option<A>> =>
Equivalence.make((x, y) => isNone(x) ? isNone(y) : isNone(y) ? false : isEquivalent(x.value, y.value))
/**
* Creates an `Order` instance for comparing `Option` values, using a provided
* `Order` for the inner type.
*
* **Details**
*
* This function produces an `Order` instance for `Option<A>`, allowing `Option`
* values to be compared:
*
* - `None` is always considered less than any `Some` value.
* - If both are `Some`, their inner values are compared using the provided
* `Order` instance.
*
* @example
* ```ts
* import { Number, Option } from "effect"
*
* const order = Option.getOrder(Number.Order)
*
* console.log(order(Option.none(), Option.none()))
* // Output: 0
*
* console.log(order(Option.none(), Option.some(1)))
* // Output: -1
*
* console.log(order(Option.some(1), Option.none()))
* // Output: 1
*
* console.log(order(Option.some(1), Option.some(2)))
* // Output: -1
*
* console.log(order(Option.some(1), Option.some(1)))
* // Output: 0
* ```
*
* @category Sorting
* @since 2.0.0
*/
export const getOrder = <A>(O: Order<A>): Order<Option<A>> =>
order.make((self, that) => isSome(self) ? (isSome(that) ? O(self.value, that.value) : 1) : -1)
/**
* Lifts a binary function to work with `Option` values, allowing the function
* to operate on two `Option`s.
*
* **Details**
*
* This function takes a binary function `f` and returns a new function that
* applies `f` to the values of two `Option`s (`self` and `that`). If both
* `Option`s are `Some`, the binary function `f` is applied to their values, and
* the result is wrapped in a new `Some`. If either `Option` is `None`, the
* result is `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // A binary function to add two numbers
* const add = (a: number, b: number): number => a + b
*
* // Lift the `add` function to work with `Option` values
* const addOptions = Option.lift2(add)
*
* // Both `Option`s are `Some`
* console.log(addOptions(Option.some(2), Option.some(3)))
* // Output: { _id: 'Option', _tag: 'Some', value: 5 }
*
* // One `Option` is `None`
* console.log(addOptions(Option.some(2), Option.none()))
* // Output: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Lifting
* @since 2.0.0
*/
export const lift2 = <A, B, C>(f: (a: A, b: B) => C): {
(that: Option<B>): (self: Option<A>) => Option<C>
(self: Option<A>, that: Option<B>): Option<C>
} => dual(2, (self: Option<A>, that: Option<B>): Option<C> => zipWith(self, that, f))
/**
* Lifts a `Predicate` or `Refinement` into the `Option` context, returning a
* `Some` of the input value if the predicate is satisfied, or `None` otherwise.
*
* **Details**
*
* This function transforms a `Predicate` (or a more specific `Refinement`) into
* a function that produces an `Option`. If the predicate evaluates to `true`,
* the input value is wrapped in a `Some`. If the predicate evaluates to
* `false`, the result is `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Check if a number is positive
* const isPositive = (n: number) => n > 0
*
* // ┌─── (b: number) => Option<number>
* // ▼
* const parsePositive = Option.liftPredicate(isPositive)
*
* console.log(parsePositive(1))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parsePositive(-1))
* // OUtput: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Lifting
* @since 2.0.0
*/
export const liftPredicate: { // Note: I intentionally avoid using the NoInfer pattern here.
<A, B extends A>(refinement: Refinement<A, B>): (a: A) => Option<B>
/**
* Lifts a `Predicate` or `Refinement` into the `Option` context, returning a
* `Some` of the input value if the predicate is satisfied, or `None` otherwise.
*
* **Details**
*
* This function transforms a `Predicate` (or a more specific `Refinement`) into
* a function that produces an `Option`. If the predicate evaluates to `true`,
* the input value is wrapped in a `Some`. If the predicate evaluates to
* `false`, the result is `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Check if a number is positive
* const isPositive = (n: number) => n > 0
*
* // ┌─── (b: number) => Option<number>
* // ▼
* const parsePositive = Option.liftPredicate(isPositive)
*
* console.log(parsePositive(1))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parsePositive(-1))
* // OUtput: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Lifting
* @since 2.0.0
*/
<B extends A, A = B>(predicate: Predicate<A>): (b: B) => Option<B>
/**
* Lifts a `Predicate` or `Refinement` into the `Option` context, returning a
* `Some` of the input value if the predicate is satisfied, or `None` otherwise.
*
* **Details**
*
* This function transforms a `Predicate` (or a more specific `Refinement`) into
* a function that produces an `Option`. If the predicate evaluates to `true`,
* the input value is wrapped in a `Some`. If the predicate evaluates to
* `false`, the result is `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Check if a number is positive
* const isPositive = (n: number) => n > 0
*
* // ┌─── (b: number) => Option<number>
* // ▼
* const parsePositive = Option.liftPredicate(isPositive)
*
* console.log(parsePositive(1))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parsePositive(-1))
* // OUtput: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Lifting
* @since 2.0.0
*/
<A, B extends A>(self: A, refinement: Refinement<A, B>): Option<B>
/**
* Lifts a `Predicate` or `Refinement` into the `Option` context, returning a
* `Some` of the input value if the predicate is satisfied, or `None` otherwise.
*
* **Details**
*
* This function transforms a `Predicate` (or a more specific `Refinement`) into
* a function that produces an `Option`. If the predicate evaluates to `true`,
* the input value is wrapped in a `Some`. If the predicate evaluates to
* `false`, the result is `None`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* // Check if a number is positive
* const isPositive = (n: number) => n > 0
*
* // ┌─── (b: number) => Option<number>
* // ▼
* const parsePositive = Option.liftPredicate(isPositive)
*
* console.log(parsePositive(1))
* // Output: { _id: 'Option', _tag: 'Some', value: 1 }
*
* console.log(parsePositive(-1))
* // OUtput: { _id: 'Option', _tag: 'None' }
* ```
*
* @category Lifting
* @since 2.0.0
*/
<B extends A, A = B>(self: B, predicate: Predicate<A>): Option<B>
} = dual(
2,
<B extends A, A = B>(b: B, predicate: Predicate<A>): Option<B> => predicate(b) ? some(b) : none()
)
/**
* Returns a function that checks if an `Option` contains a specified value,
* using a provided equivalence function.
*
* **Details**
*
* This function allows you to check whether an `Option` contains a specific
* value. It uses an equivalence function `isEquivalent` to compare the value
* inside the `Option` to the provided value. If the `Option` is `Some` and the
* equivalence function returns `true`, the result is `true`. If the `Option` is
* `None` or the values are not equivalent, the result is `false`.
*
* @example
* ```ts
* import { Number, Option } from "effect"
*
* const contains = Option.containsWith(Number.Equivalence)
*
* console.log(Option.some(2).pipe(contains(2)))
* // Output: true
*
* console.log(Option.some(1).pipe(contains(2)))
* // Output: false
*
* console.log(Option.none().pipe(contains(2)))
* // Output: false
* ```
*
* @see {@link contains} for a version that uses the default `Equivalence`.
*
* @category Elements
* @since 2.0.0
*/
export const containsWith = <A>(isEquivalent: (self: A, that: A) => boolean): {
(a: A): (self: Option<A>) => boolean
(self: Option<A>, a: A): boolean
} => dual(2, (self: Option<A>, a: A): boolean => isNone(self) ? false : isEquivalent(self.value, a))
const _equivalence = Equal.equivalence()
/**
* Returns a function that checks if an `Option` contains a specified value
* using the default `Equivalence`.
*
* **Details**
*
* This function allows you to check whether an `Option` contains a specific
* value. It uses the default `Equivalence` for equality comparison. If the
* `Option` is `Some` and its value is equivalent to the provided value, the
* result is `true`. If the `Option` is `None` or the values are not equivalent,
* the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(2).pipe(Option.contains(2)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.contains(2)))
* // Output: false
*
* console.log(Option.none().pipe(Option.contains(2)))
* // Output: false
* ```
*
* @see {@link containsWith} for a version that allows you to specify a custom equivalence function.
*
* @category Elements
* @since 2.0.0
*/
export const contains: {
/**
* Returns a function that checks if an `Option` contains a specified value
* using the default `Equivalence`.
*
* **Details**
*
* This function allows you to check whether an `Option` contains a specific
* value. It uses the default `Equivalence` for equality comparison. If the
* `Option` is `Some` and its value is equivalent to the provided value, the
* result is `true`. If the `Option` is `None` or the values are not equivalent,
* the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(2).pipe(Option.contains(2)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.contains(2)))
* // Output: false
*
* console.log(Option.none().pipe(Option.contains(2)))
* // Output: false
* ```
*
* @see {@link containsWith} for a version that allows you to specify a custom equivalence function.
*
* @category Elements
* @since 2.0.0
*/
<A>(a: A): (self: Option<A>) => boolean
/**
* Returns a function that checks if an `Option` contains a specified value
* using the default `Equivalence`.
*
* **Details**
*
* This function allows you to check whether an `Option` contains a specific
* value. It uses the default `Equivalence` for equality comparison. If the
* `Option` is `Some` and its value is equivalent to the provided value, the
* result is `true`. If the `Option` is `None` or the values are not equivalent,
* the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* console.log(Option.some(2).pipe(Option.contains(2)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.contains(2)))
* // Output: false
*
* console.log(Option.none().pipe(Option.contains(2)))
* // Output: false
* ```
*
* @see {@link containsWith} for a version that allows you to specify a custom equivalence function.
*
* @category Elements
* @since 2.0.0
*/
<A>(self: Option<A>, a: A): boolean
} = containsWith(_equivalence)
/**
* Checks if a value in an `Option` satisfies a given predicate or refinement.
*
* **Details**
*
* This function allows you to check if a value inside a `Some` meets a
* specified condition. If the `Option` is `None`, the result is `false`. If the
* `Option` is `Some`, the provided predicate or refinement is applied to the
* value:
*
* - If the condition is met, the result is `true`.
* - If the condition is not met, the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const isEven = (n: number) => n % 2 === 0
*
* console.log(Option.some(2).pipe(Option.exists(isEven)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.exists(isEven)))
* // Output: false
*
* console.log(Option.none().pipe(Option.exists(isEven)))
* // Output: false
* ```
*
* @category Elements
* @since 2.0.0
*/
export const exists: {
/**
* Checks if a value in an `Option` satisfies a given predicate or refinement.
*
* **Details**
*
* This function allows you to check if a value inside a `Some` meets a
* specified condition. If the `Option` is `None`, the result is `false`. If the
* `Option` is `Some`, the provided predicate or refinement is applied to the
* value:
*
* - If the condition is met, the result is `true`.
* - If the condition is not met, the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const isEven = (n: number) => n % 2 === 0
*
* console.log(Option.some(2).pipe(Option.exists(isEven)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.exists(isEven)))
* // Output: false
*
* console.log(Option.none().pipe(Option.exists(isEven)))
* // Output: false
* ```
*
* @category Elements
* @since 2.0.0
*/
<A, B extends A>(refinement: Refinement<NoInfer<A>, B>): (self: Option<A>) => self is Option<B>
/**
* Checks if a value in an `Option` satisfies a given predicate or refinement.
*
* **Details**
*
* This function allows you to check if a value inside a `Some` meets a
* specified condition. If the `Option` is `None`, the result is `false`. If the
* `Option` is `Some`, the provided predicate or refinement is applied to the
* value:
*
* - If the condition is met, the result is `true`.
* - If the condition is not met, the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const isEven = (n: number) => n % 2 === 0
*
* console.log(Option.some(2).pipe(Option.exists(isEven)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.exists(isEven)))
* // Output: false
*
* console.log(Option.none().pipe(Option.exists(isEven)))
* // Output: false
* ```
*
* @category Elements
* @since 2.0.0
*/
<A>(predicate: Predicate<NoInfer<A>>): (self: Option<A>) => boolean
/**
* Checks if a value in an `Option` satisfies a given predicate or refinement.
*
* **Details**
*
* This function allows you to check if a value inside a `Some` meets a
* specified condition. If the `Option` is `None`, the result is `false`. If the
* `Option` is `Some`, the provided predicate or refinement is applied to the
* value:
*
* - If the condition is met, the result is `true`.
* - If the condition is not met, the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const isEven = (n: number) => n % 2 === 0
*
* console.log(Option.some(2).pipe(Option.exists(isEven)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.exists(isEven)))
* // Output: false
*
* console.log(Option.none().pipe(Option.exists(isEven)))
* // Output: false
* ```
*
* @category Elements
* @since 2.0.0
*/
<A, B extends A>(self: Option<A>, refinement: Refinement<A, B>): self is Option<B>
/**
* Checks if a value in an `Option` satisfies a given predicate or refinement.
*
* **Details**
*
* This function allows you to check if a value inside a `Some` meets a
* specified condition. If the `Option` is `None`, the result is `false`. If the
* `Option` is `Some`, the provided predicate or refinement is applied to the
* value:
*
* - If the condition is met, the result is `true`.
* - If the condition is not met, the result is `false`.
*
* @example
* ```ts
* import { Option } from "effect"
*
* const isEven = (n: number) => n % 2 === 0
*
* console.log(Option.some(2).pipe(Option.exists(isEven)))
* // Output: true
*
* console.log(Option.some(1).pipe(Option.exists(isEven)))
* // Output: false
*
* console.log(Option.none().pipe(Option.exists(isEven)))
* // Output: false
* ```
*
* @category Elements
* @since 2.0.0
*/
<A>(self: Option<A>, predicate: Predicate<A>): boolean
} = dual(
2,
<A, B extends A>(self: Option<A>, refinement: Refinement<A, B>): self is Option<B> =>
isNone(self) ? false : refinement(self.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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ 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: {
// -------------------------------------------------------------------------------------
// 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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link Do}
* @see {@link bind}
* @see {@link let_ let}
*
* @category Do notation
* @since 2.0.0
*/
<N extends string>(name: N): <A>(self: Option<A>) => Option<{ [K in N]: A }>
// -------------------------------------------------------------------------------------
// 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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link Do}
* @see {@link bind}
* @see {@link let_ let}
*
* @category Do notation
* @since 2.0.0
*/
<A, N extends string>(self: Option<A>, name: N): Option<{ [K in N]: A }>
} = doNotation.bindTo<OptionTypeLambda>(map)
const let_: {
<N extends string, A extends object, B>(
name: Exclude<N, keyof A>,
f: (a: NoInfer<A>) => B
): (self: Option<A>) => Option<{ [K in N | keyof A]: K extends keyof A ? A[K] : B }>
<A extends object, N extends string, B>(
self: Option<A>,
name: Exclude<N, keyof A>,
f: (a: NoInfer<A>) => B
): Option<{ [K in N | keyof A]: K extends keyof A ? A[K] : B }>
} = doNotation.let_<OptionTypeLambda>(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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link Do}
* @see {@link bind}
* @see {@link bindTo}
*
* @category Do notation
* @since 2.0.0
*/
let_ as let
}
/**
* 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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ 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: {
/**
* 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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link Do}
* @see {@link bindTo}
* @see {@link let_ let}
*
* @category Do notation
* @since 2.0.0
*/
<N extends string, A extends object, B>(name: Exclude<N, keyof A>, f: (a: NoInfer<A>) => Option<B>): (self: Option<A>) => Option<{ [K in N | keyof A]: K extends keyof A ? A[K] : B }>
/**
* 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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link Do}
* @see {@link bindTo}
* @see {@link let_ let}
*
* @category Do notation
* @since 2.0.0
*/
<A extends object, N extends string, B>(
self: Option<A>,
name: Exclude<N, keyof A>,
f: (a: NoInfer<A>) => Option<B>
): Option<{ [K in N | keyof A]: K extends keyof A ? A[K] : B }>
} = doNotation.bind<OptionTypeLambda>(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 `Option` 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
* 5. Regular `Option` functions like `map` and `filter` can still be used within the do simulation. These functions will receive the accumulated variables as arguments within the scope
*
* @example
* ```ts
* import * as assert from "node:assert"
* import { Option, pipe } from "effect"
*
* const result = pipe(
* Option.Do,
* Option.bind("x", () => Option.some(2)),
* Option.bind("y", () => Option.some(3)),
* Option.let("sum", ({ x, y }) => x + y),
* Option.filter(({ x, y }) => x * y > 5)
* )
* assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))
* ```
*
* @see {@link bindTo}
* @see {@link bind}
* @see {@link let_ let}
*
* @category Do notation
* @since 2.0.0
*/
export const Do: Option<{}> = some({})
const adapter = Gen.adapter<OptionTypeLambda>()
/**
* Similar to `Effect.gen`, `Option.gen` provides a more readable,
* generator-based syntax for working with `Option` values, making code that
* involves `Option` easier to write and understand. This approach is similar to
* using `async/await` but tailored for `Option`.
*
* **Example** (Using `Option.gen` to Create a Combined Value)
*
* ```ts
* import { Option } from "effect"
*
* const maybeName: Option.Option<string> = Option.some("John")
* const maybeAge: Option.Option<number> = Option.some(25)
*
* const person = Option.gen(function* () {
* const name = (yield* maybeName).toUpperCase()
* const age = yield* maybeAge
* return { name, age }
* })
*
* console.log(person)
* // Output:
* // { _id: 'Option', _tag: 'Some', value: { name: 'JOHN', age: 25 } }
* ```
*
* @category Generators
* @since 2.0.0
*/
export const gen: Gen.Gen<OptionTypeLambda, Gen.Adapter<OptionTypeLambda>> = (...args) => {
const f = args.length === 1 ? args[0] : args[1].bind(args[0])
const iterator = f(adapter)
let state: IteratorResult<any> = iterator.next()
while (!state.done) {
const current = Gen.isGenKind(state.value)
? state.value.value
: Gen.yieldWrapGet(state.value)
if (isNone(current)) {
return current
}
state = iterator.next(current.value as never)
}
return some(state.value)
}
/**
* Merges two optional values, applying a function if both exist.
* Unlike {@link zipWith}, this function returns `None` only if both inputs are `None`.
*
* @internal
*/
export const mergeWith = <A>(f: (a1: A, a2: A) => A) => (o1: Option<A>, o2: Option<A>): Option<A> => {
if (isNone(o1)) {
return o2
} else if (isNone(o2)) {
return o1
}
return some(f(o1.value, o2.value))
}
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