<K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(
self: ReadonlyRecord<K, A>
) => Option.Option<Record<K, A | B>>
<K extends string | symbol, A, B>(
self: ReadonlyRecord<K, A>,
key: NoInfer<K>,
b: B
): Option.Option<Record<K, A | B>>Replaces the value at an existing key safely and returns the updated record in
Option.some.
Details
If the key is not present, returns Option.none() and leaves the record
unchanged.
Example (Replacing a value at a key)
import { Record } from "effect"
Record.replace({ a: 1, b: 2, c: 3 }, "a", 10) // Option.some({ a: 10, b: 2, c: 3 })
Record.replace(Record.empty<string>(), "a", 10) // Option.none()export const const replace: {
<K extends string | symbol, B>(
key: NoInfer<K>,
b: B
): <A>(
self: ReadonlyRecord<K, A>
) => Option.Option<Record<K, A | B>>
<K extends string | symbol, A, B>(
self: ReadonlyRecord<K, A>,
key: NoInfer<K>,
b: B
): Option.Option<Record<K, A | B>>
}
Replaces the value at an existing key safely and returns the updated record in
Option.some.
Details
If the key is not present, returns Option.none() and leaves the record
unchanged.
Example (Replacing a value at a key)
import { Record } from "effect"
Record.replace({ a: 1, b: 2, c: 3 }, "a", 10) // Option.some({ a: 10, b: 2, c: 3 })
Record.replace(Record.empty<string>(), "a", 10) // Option.none()
replace: {
<function (type parameter) K in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>K extends string | symbol, function (type parameter) B in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>B>(
key: NoInfer<K>key: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) K in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>K>,
b: Bb: function (type parameter) B in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>B
): <function (type parameter) A in <A>(self: ReadonlyRecord<K, A>): Option.Option<Record<K, A | B>>A>(self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>K, function (type parameter) A in <A>(self: ReadonlyRecord<K, A>): Option.Option<Record<K, 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 Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<function (type parameter) K in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>K, function (type parameter) A in <A>(self: ReadonlyRecord<K, A>): Option.Option<Record<K, A | B>>A | function (type parameter) B in <K extends string | symbol, B>(key: NoInfer<K>, b: B): <A>(self: ReadonlyRecord<K, A>) => Option.Option<Record<K, A | B>>B>>
<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K extends string | symbol, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A, function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>B>(
self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A>,
key: NoInfer<K>key: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K>,
b: Bb: function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, 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 Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A | function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>B>>
} = dual<(...args: Array<any>) => any, <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B) => Option.Option<Record<K, A | B>>>(arity: 3, body: <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B) => Option.Option<Record<K, A | B>>): ((...args: Array<any>) => any) & (<K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B) => Option.Option<Record<K, 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) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K extends string | symbol, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A, function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>B>(
self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A>,
key: NoInfer<K>key: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K>,
b: Bb: function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, 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 Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<function (type parameter) K in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>K, function (type parameter) A in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>A | function (type parameter) B in <K extends string | symbol, A, B>(self: ReadonlyRecord<K, A>, key: NoInfer<K>, b: B): Option.Option<Record<K, A | B>>B>> => const modify: {
<K extends string | symbol, A, B>(
key: NoInfer<K>,
f: (a: A) => B
): (
self: ReadonlyRecord<K, A>
) => Option.Option<Record<K, A | B>>
<K extends string | symbol, A, B>(
self: ReadonlyRecord<K, A>,
key: NoInfer<K>,
f: (a: A) => B
): Option.Option<Record<K, A | B>>
}
self: ReadonlyRecord<K, A>self, key: NoInfer<K>key, () => b: Bb)
)