<B>(i: number, b: B): <A>(
self: Iterable<A>
) => Option.Option<NonEmptyArray<A | B>>
<A, B>(self: Iterable<A>, i: number, b: B): Option.Option<
NonEmptyArray<A | B>
>Inserts an element at the specified index safely, returning a new NonEmptyArray
wrapped in an Option.
When to use
Use to insert a single element at a specific position in an array.
Details
Valid indices are 0 to length, inclusive. Inserting at length appends.
Example (Inserting at an index)
import { Array } from "effect"
console.log(Array.insertAt(["a", "b", "c", "e"], 3, "d")) // Option.some(["a", "b", "c", "d", "e"])export const const insertAt: {
<B>(i: number, b: B): <A>(
self: Iterable<A>
) => Option.Option<NonEmptyArray<A | B>>
<A, B>(
self: Iterable<A>,
i: number,
b: B
): Option.Option<NonEmptyArray<A | B>>
}
Inserts an element at the specified index safely, returning a new NonEmptyArray
wrapped in an Option.
When to use
Use to insert a single element at a specific position in an array.
Details
Valid indices are 0 to length, inclusive. Inserting at length appends.
Example (Inserting at an index)
import { Array } from "effect"
console.log(Array.insertAt(["a", "b", "c", "e"], 3, "d")) // Option.some(["a", "b", "c", "d", "e"])
insertAt: {
<function (type parameter) B in <B>(i: number, b: B): <A>(self: Iterable<A>) => Option.Option<NonEmptyArray<A | B>>B>(i: numberi: number, b: Bb: function (type parameter) B in <B>(i: number, b: B): <A>(self: Iterable<A>) => Option.Option<NonEmptyArray<A | B>>B): <function (type parameter) A in <A>(self: Iterable<A>): Option.Option<NonEmptyArray<A | B>>A>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A>(self: Iterable<A>): Option.Option<NonEmptyArray<A | B>>A>) => import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A>(self: Iterable<A>): Option.Option<NonEmptyArray<A | B>>A | function (type parameter) B in <B>(i: number, b: B): <A>(self: Iterable<A>) => Option.Option<NonEmptyArray<A | B>>B>>
<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A, function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A>, i: numberi: number, b: Bb: function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B): import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A | function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B>>
} = dual<(...args: Array<any>) => any, <A, B>(self: Iterable<A>, i: number, b: B) => Option.Option<NonEmptyArray<A | B>>>(arity: 3, body: <A, B>(self: Iterable<A>, i: number, b: B) => Option.Option<NonEmptyArray<A | B>>): ((...args: Array<any>) => any) & (<A, B>(self: Iterable<A>, i: number, b: B) => Option.Option<NonEmptyArray<A | B>>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(3, <function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A, function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A>, i: numberi: number, b: Bb: function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B): import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A | function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B>> => {
const const out: (A | B)[]out: interface Array<T>Array<function (type parameter) A in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>A | function (type parameter) B in <A, B>(self: Iterable<A>, i: number, b: B): Option.Option<NonEmptyArray<A | B>>B> = const Array: ArrayConstructorExposes the global array constructor.
When to use
Use to access native JavaScript array constructor methods such as isArray
or from from the Effect module namespace.
Example (Accessing the Array constructor)
import { Array } from "effect"
const arr = new Array.Array(3)
console.log(arr) // [undefined, undefined, undefined]
Array.ArrayConstructor.from<A>(iterable: Iterable<A> | ArrayLike<A>): A[] (+3 overloads)Creates an array from an iterable object.
from(self: Iterable<A>self) // copy because `splice` mutates the array
if (i: numberi < 0 || i: numberi > const out: (A | B)[]out.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length) {
return import OptionOption.const none: <A = never>() => Option<A>Creates an Option representing the absence of a value.
When to use
Use to represent a missing or uninitialized value, such as returning "no
result" from a function.
Details
- Returns
Option<never>, which is a subtype of Option<A> for any A
- Always returns the same singleton instance
Example (Creating an empty Option)
import { Option } from "effect"
// ┌─── Option<never>
// ▼
const noValue = Option.none()
console.log(noValue)
// Output: { _id: 'Option', _tag: 'None' }
none()
}
const out: (A | B)[]out.Array<A | B>.splice(start: number, deleteCount: number, ...items: (A | B)[]): (A | B)[] (+1 overload)Removes elements from an array and, if necessary, inserts new elements in their place, returning the deleted elements.
splice(i: numberi, 0, b: Bb)
return import OptionOption.const some: <A>(value: A) => Option<A>Wraps the given value into an Option to represent its presence.
When to use
Use to wrap a known present value as Option
- Returning a successful result from a partial function
Details
- Always returns
Some<A>
- Does not filter
null or undefined; use
fromNullishOr
for that
Example (Wrapping a value)
import { Option } from "effect"
// ┌─── Option<number>
// ▼
const value = Option.some(1)
console.log(value)
// Output: { _id: 'Option', _tag: 'Some', value: 1 }
some(const out: (A | B)[]out as any)
})