<A>(f: (a: A) => A): (self: Ref<A>) => Effect.Effect<void>
<A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void>Updates the value of the Ref atomically using the given function.
When to use
Use to apply a Ref state transition without returning a value.
Example (Updating a value)
import { Effect, Ref } from "effect"
const program = Effect.gen(function*() {
const counter = yield* Ref.make(5)
// Update the value
yield* Ref.update(counter, (n) => n * 2)
const value = yield* Ref.get(counter)
console.log(value) // 10
})
// Using multiple operations
const program2 = Effect.gen(function*() {
const counter = yield* Ref.make(5)
yield* Ref.update(counter, (n: number) => n + 10)
const value = yield* Ref.get(counter)
console.log(value) // 15
})export const const update: (<A>(
f: (a: A) => A
) => (self: Ref<A>) => Effect.Effect<void>) &
(<A>(
self: Ref<A>,
f: (a: A) => A
) => Effect.Effect<void>)
Updates the value of the Ref atomically using the given function.
When to use
Use to apply a Ref state transition without returning a value.
Example (Updating a value)
import { Effect, Ref } from "effect"
const program = Effect.gen(function*() {
const counter = yield* Ref.make(5)
// Update the value
yield* Ref.update(counter, (n) => n * 2)
const value = yield* Ref.get(counter)
console.log(value) // 10
})
// Using multiple operations
const program2 = Effect.gen(function*() {
const counter = yield* Ref.make(5)
yield* Ref.update(counter, (n: number) => n + 10)
const value = yield* Ref.get(counter)
console.log(value) // 15
})
update = dual<<A>(f: (a: A) => A) => (self: Ref<A>) => Effect.Effect<void>, <A>(self: Ref<A>, f: (a: A) => A) => Effect.Effect<void>>(arity: 2, body: <A>(self: Ref<A>, f: (a: A) => A) => Effect.Effect<void>): (<A>(f: (a: A) => A) => (self: Ref<A>) => Effect.Effect<void>) & (<A>(self: Ref<A>, f: (a: A) => A) => Effect.Effect<void>) (+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<
<function (type parameter) A in <A>(f: (a: A) => A): (self: Ref<A>) => Effect.Effect<void>A>(f: (a: A) => Af: (a: Aa: function (type parameter) A in <A>(f: (a: A) => A): (self: Ref<A>) => Effect.Effect<void>A) => function (type parameter) A in <A>(f: (a: A) => A): (self: Ref<A>) => Effect.Effect<void>A) => (self: Ref<A>(parameter) self: {
ref: MutableRef.MutableRef<A>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Ref<in out A>A mutable reference that provides atomic read, write, and update operations.
When to use
Use to keep shared mutable state that is read and updated inside Effect
programs.
Details
A Ref is a thread-safe mutable reference type for shared state. It supports
simple read and write operations as well as atomic transformations.
Example (Reading and updating a ref)
import { Effect, Ref } from "effect"
const program = Effect.gen(function*() {
// Create a ref with initial value
const counter = yield* Ref.make(0)
// Read the current value
const value = yield* Ref.get(counter)
console.log(value) // 0
// Update the value atomically
yield* Ref.update(counter, (n) => n + 1)
// Read the updated value
const newValue = yield* Ref.get(counter)
console.log(newValue) // 1
})
The Ref namespace containing type definitions and utilities.
When to use
Use when referring to type members nested under the Ref namespace.
Ref<function (type parameter) A in <A>(f: (a: A) => A): (self: Ref<A>) => Effect.Effect<void>A>) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<void>,
<function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void>A>(self: Ref<A>(parameter) self: {
ref: MutableRef.MutableRef<A>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Ref<in out A>A mutable reference that provides atomic read, write, and update operations.
When to use
Use to keep shared mutable state that is read and updated inside Effect
programs.
Details
A Ref is a thread-safe mutable reference type for shared state. It supports
simple read and write operations as well as atomic transformations.
Example (Reading and updating a ref)
import { Effect, Ref } from "effect"
const program = Effect.gen(function*() {
// Create a ref with initial value
const counter = yield* Ref.make(0)
// Read the current value
const value = yield* Ref.get(counter)
console.log(value) // 0
// Update the value atomically
yield* Ref.update(counter, (n) => n + 1)
// Read the updated value
const newValue = yield* Ref.get(counter)
console.log(newValue) // 1
})
The Ref namespace containing type definitions and utilities.
When to use
Use when referring to type members nested under the Ref namespace.
Ref<function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void>A>, f: (a: A) => Af: (a: Aa: function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void>A) => function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void>A) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<void>
>(2, <function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void, never, never>A>(self: Ref<A>(parameter) self: {
ref: MutableRef.MutableRef<A>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Ref<in out A>A mutable reference that provides atomic read, write, and update operations.
When to use
Use to keep shared mutable state that is read and updated inside Effect
programs.
Details
A Ref is a thread-safe mutable reference type for shared state. It supports
simple read and write operations as well as atomic transformations.
Example (Reading and updating a ref)
import { Effect, Ref } from "effect"
const program = Effect.gen(function*() {
// Create a ref with initial value
const counter = yield* Ref.make(0)
// Read the current value
const value = yield* Ref.get(counter)
console.log(value) // 0
// Update the value atomically
yield* Ref.update(counter, (n) => n + 1)
// Read the updated value
const newValue = yield* Ref.get(counter)
console.log(newValue) // 1
})
The Ref namespace containing type definitions and utilities.
When to use
Use when referring to type members nested under the Ref namespace.
Ref<function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void, never, never>A>, f: (a: A) => Af: (a: Aa: function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void, never, never>A) => function (type parameter) A in <A>(self: Ref<A>, f: (a: A) => A): Effect.Effect<void, never, never>A) =>
import EffectEffect.const sync: <A>(
thunk: LazyArg<A>
) => Effect<A>
Creates an Effect that represents a synchronous side-effectful computation.
When to use
Use when you need to wrap a synchronous side-effectful operation that is not
expected to throw.
Details
The provided function is evaluated lazily when the effect runs.
Gotchas
The function must not throw. If it throws, the thrown value is treated as a
defect, not as a typed failure. Use try when throwing is expected.
Example (Capturing synchronous logging in an Effect)
import { Effect } from "effect"
const log = (message: string) =>
Effect.sync(() => {
console.log(message) // side effect
})
// ┌─── Effect<void, never, never>
// ▼
const program = log("Hello, World!")
sync(() => {
self: Ref<A>(parameter) self: {
ref: MutableRef.MutableRef<A>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Ref<A>.ref: MutableRef.MutableRef<A>(property) Ref<A>.ref: {
current: T;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
MutableRef<A>.current: Acurrent = f: (a: A) => Af(self: Ref<A>(parameter) self: {
ref: MutableRef.MutableRef<A>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Ref<A>.ref: MutableRef.MutableRef<A>(property) Ref<A>.ref: {
current: T;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
MutableRef<A>.current: Acurrent)
}))