<K>(key: K): <A, E>(self: RcMap<K, A, E>) => Effect.Effect<void>
<K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>Extends the idle time for a resource in the RcMap. If the RcMap has an
idleTimeToLive configured, calling touch will reset the expiration
timer for the specified key.
When to use
Use to keep an idle resource alive longer without acquiring a new reference.
Example (Extending resource idle time)
import { Effect, RcMap } from "effect"
Effect.gen(function*() {
const map = yield* RcMap.make({
lookup: (key: string) =>
Effect.acquireRelease(
Effect.succeed(`Resource: ${key}`),
() => Effect.log(`Released ${key}`)
),
idleTimeToLive: "10 seconds"
})
// Get a resource
yield* RcMap.get(map, "session")
// Touch the resource to extend its idle time
// This resets the 10-second expiration timer
yield* RcMap.touch(map, "session")
// The resource will now live for another 10 seconds
// from the time it was touched
}).pipe(Effect.scoped)export const const touch: {
<K>(key: K): <A, E>(
self: RcMap<K, A, E>
) => Effect.Effect<void>
<K, A, E>(
self: RcMap<K, A, E>,
key: K
): Effect.Effect<void>
}
Extends the idle time for a resource in the RcMap. If the RcMap has an
idleTimeToLive configured, calling touch will reset the expiration
timer for the specified key.
When to use
Use to keep an idle resource alive longer without acquiring a new reference.
Example (Extending resource idle time)
import { Effect, RcMap } from "effect"
Effect.gen(function*() {
const map = yield* RcMap.make({
lookup: (key: string) =>
Effect.acquireRelease(
Effect.succeed(`Resource: ${key}`),
() => Effect.log(`Released ${key}`)
),
idleTimeToLive: "10 seconds"
})
// Get a resource
yield* RcMap.get(map, "session")
// Touch the resource to extend its idle time
// This resets the 10-second expiration timer
yield* RcMap.touch(map, "session")
// The resource will now live for another 10 seconds
// from the time it was touched
}).pipe(Effect.scoped)
touch: {
<function (type parameter) K in <K>(key: K): <A, E>(self: RcMap<K, A, E>) => Effect.Effect<void>K>(key: Kkey: function (type parameter) K in <K>(key: K): <A, E>(self: RcMap<K, A, E>) => Effect.Effect<void>K): <function (type parameter) A in <A, E>(self: RcMap<K, A, E>): Effect.Effect<void>A, function (type parameter) E in <A, E>(self: RcMap<K, A, E>): Effect.Effect<void>E>(self: RcMap<K, A, E>(parameter) self: {
lookup: (key: K) => Effect.Effect<A, E, Scope.Scope>;
context: Context.Context<never>;
scope: Scope.Scope;
idleTimeToLive: (key: K) => Duration.Duration;
capacity: number;
state: State<K, A, E>;
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 RcMap<in out K, in out A, in out E = never>An RcMap is a reference-counted map data structure that manages the lifecycle
of resources indexed by keys. Resources are lazily acquired and automatically
released when no longer in use.
When to use
Use to share scoped resources by key while automatically releasing them after
their last active reference is gone.
Example (Inspecting a reference-counted map)
import { Effect, RcMap } from "effect"
Effect.gen(function*() {
// Create an RcMap that manages database connections
const dbConnectionMap = yield* RcMap.make({
lookup: (dbName: string) =>
Effect.acquireRelease(
Effect.succeed(`Connection to ${dbName}`),
(conn) => Effect.log(`Closing ${conn}`)
),
capacity: 10,
idleTimeToLive: "5 minutes"
})
// The RcMap interface provides access to:
// - lookup: Function to acquire resources
// - capacity: Maximum number of resources
// - idleTimeToLive: Time before idle resources are released
// - state: Current state of the map
console.log(`Capacity: ${dbConnectionMap.capacity}`)
}).pipe(Effect.scoped)
RcMap<function (type parameter) K in <K>(key: K): <A, E>(self: RcMap<K, A, E>) => Effect.Effect<void>K, function (type parameter) A in <A, E>(self: RcMap<K, A, E>): Effect.Effect<void>A, function (type parameter) E in <A, E>(self: RcMap<K, A, E>): Effect.Effect<void>E>) => 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) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>E>(self: RcMap<K, A, E>(parameter) self: {
lookup: (key: K) => Effect.Effect<A, E, Scope.Scope>;
context: Context.Context<never>;
scope: Scope.Scope;
idleTimeToLive: (key: K) => Duration.Duration;
capacity: number;
state: State<K, A, E>;
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 RcMap<in out K, in out A, in out E = never>An RcMap is a reference-counted map data structure that manages the lifecycle
of resources indexed by keys. Resources are lazily acquired and automatically
released when no longer in use.
When to use
Use to share scoped resources by key while automatically releasing them after
their last active reference is gone.
Example (Inspecting a reference-counted map)
import { Effect, RcMap } from "effect"
Effect.gen(function*() {
// Create an RcMap that manages database connections
const dbConnectionMap = yield* RcMap.make({
lookup: (dbName: string) =>
Effect.acquireRelease(
Effect.succeed(`Connection to ${dbName}`),
(conn) => Effect.log(`Closing ${conn}`)
),
capacity: 10,
idleTimeToLive: "5 minutes"
})
// The RcMap interface provides access to:
// - lookup: Function to acquire resources
// - capacity: Maximum number of resources
// - idleTimeToLive: Time before idle resources are released
// - state: Current state of the map
console.log(`Capacity: ${dbConnectionMap.capacity}`)
}).pipe(Effect.scoped)
RcMap<function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>E>, key: Kkey: function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void>K): 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>
} = dual<(...args: Array<any>) => any, <K, A, E>(self: RcMap<K, A, E>, key: K) => Effect.Effect<void, never, never>>(arity: 2, body: <K, A, E>(self: RcMap<K, A, E>, key: K) => Effect.Effect<void, never, never>): ((...args: Array<any>) => any) & (<K, A, E>(self: RcMap<K, A, E>, key: K) => Effect.Effect<void, never, never>) (+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(
2,
<function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>E>(self: RcMap<K, A, E>(parameter) self: {
lookup: (key: K) => Effect.Effect<A, E, Scope.Scope>;
context: Context.Context<never>;
scope: Scope.Scope;
idleTimeToLive: (key: K) => Duration.Duration;
capacity: number;
state: State<K, A, E>;
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 RcMap<in out K, in out A, in out E = never>An RcMap is a reference-counted map data structure that manages the lifecycle
of resources indexed by keys. Resources are lazily acquired and automatically
released when no longer in use.
When to use
Use to share scoped resources by key while automatically releasing them after
their last active reference is gone.
Example (Inspecting a reference-counted map)
import { Effect, RcMap } from "effect"
Effect.gen(function*() {
// Create an RcMap that manages database connections
const dbConnectionMap = yield* RcMap.make({
lookup: (dbName: string) =>
Effect.acquireRelease(
Effect.succeed(`Connection to ${dbName}`),
(conn) => Effect.log(`Closing ${conn}`)
),
capacity: 10,
idleTimeToLive: "5 minutes"
})
// The RcMap interface provides access to:
// - lookup: Function to acquire resources
// - capacity: Maximum number of resources
// - idleTimeToLive: Time before idle resources are released
// - state: Current state of the map
console.log(`Capacity: ${dbConnectionMap.capacity}`)
}).pipe(Effect.scoped)
RcMap<function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>E>, key: Kkey: function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Effect.Effect<void, never, never>K) =>
import EffectEffect.const clockWith: <A, E, R>(
f: (clock: Clock) => Effect<A, E, R>
) => Effect<A, E, R>
Retrieves the Clock service from the context and provides it to the
specified effectful function.
Example (Accessing the Clock service)
import { Console, Effect } from "effect"
const program = Effect.clockWith((clock) =>
clock.currentTimeMillis.pipe(
Effect.map((currentTime) => `Current time is: ${currentTime}`),
Effect.tap(Console.log)
)
)
Effect.runFork(program)
// Example Output:
// Current time is: 1735484929744
clockWith((clock: Clock(parameter) clock: {
currentTimeMillisUnsafe: () => number;
currentTimeMillis: Effect<number>;
currentTimeNanosUnsafe: () => bigint;
currentTimeNanos: Effect<bigint>;
sleep: (duration: Duration.Duration) => Effect<void>;
}
self: RcMap<K, A, E>(parameter) self: {
lookup: (key: K) => Effect.Effect<A, E, Scope.Scope>;
context: Context.Context<never>;
scope: Scope.Scope;
idleTimeToLive: (key: K) => Duration.Duration;
capacity: number;
state: State<K, A, E>;
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; <…;
}
RcMap<K, A, E>.state: State<K, A, E>state._tag: "Open" | "Closed"_tag === "Closed") {
return import EffectEffect.const void: Effect.Effect<void, never, never>(alias) const void: {
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;
}
Returns an effect that succeeds with void.
void
}
const const o: Option<State.Entry<A, E>>o = import MutableHashMapMutableHashMap.const get: {
<K>(key: K): <V>(
self: MutableHashMap<K, V>
) => Option.Option<V>
<K, V>(
self: MutableHashMap<K, V>,
key: K
): Option.Option<V>
}
self: RcMap<K, A, E>(parameter) self: {
lookup: (key: K) => Effect.Effect<A, E, Scope.Scope>;
context: Context.Context<never>;
scope: Scope.Scope;
idleTimeToLive: (key: K) => Duration.Duration;
capacity: number;
state: State<K, A, E>;
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; <…;
}
RcMap<K, A, E>.state: State<K, A, E>(property) RcMap<K, A, E>.state: {
_tag: "Open";
map: MutableHashMap.MutableHashMap<K, Entry<A, E>>;
}
State<K, A, E>.Open<K, A, E>.map: MutableHashMap.MutableHashMap<K, Entry<A, E>>(property) State<K, A, E>.Open<K, A, E>.map: {
backing: Map<K, V>;
buckets: Map<number, NonEmptyArray<K>>;
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;
}
key: Kkey)
if (const o: Option<State.Entry<A, E>>o._tag: "None" | "Some"_tag === "None" || import DurationDuration.const isZero: (self: Duration) => booleanChecks whether a Duration is zero.
Example (Checking for zero durations)
import { Duration } from "effect"
console.log(Duration.isZero(Duration.zero)) // true
console.log(Duration.isZero(Duration.seconds(1))) // false
isZero(const o: Some<State.Entry<A, E>>const o: {
_tag: "Some";
_op: "Some";
value: A;
valueOrUndefined: 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; <…;
toString: () => string;
toJSON: () => unknown;
}
Some<State<K, A, E>.Entry<A, E>>.value: State.Entry<A, E>(property) Some<State<K, A, E>.Entry<A, E>>.value: {
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
finalizer: Effect.Effect<void>;
idleTimeToLive: Duration.Duration;
fiber: Fiber.Fiber<void> | undefined;
expiresAt: number;
refCount: number;
}
State<K, A, E>.Entry<A, E>.idleTimeToLive: Duration.Duration(property) State<K, A, E>.Entry<A, E>.idleTimeToLive: {
value: DurationValue;
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;
}
import EffectEffect.const void: Effect.Effect<void, never, never>(alias) const void: {
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;
}
Returns an effect that succeeds with void.
void
}
const const entry: State.Entry<A, E>const entry: {
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
finalizer: Effect.Effect<void>;
idleTimeToLive: Duration.Duration;
fiber: Fiber.Fiber<void> | undefined;
expiresAt: number;
refCount: number;
}
const o: Some<State.Entry<A, E>>const o: {
_tag: "Some";
_op: "Some";
value: A;
valueOrUndefined: 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; <…;
toString: () => string;
toJSON: () => unknown;
}
Some<State<K, A, E>.Entry<A, E>>.value: State.Entry<A, E>(property) Some<State<K, A, E>.Entry<A, E>>.value: {
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
finalizer: Effect.Effect<void>;
idleTimeToLive: Duration.Duration;
fiber: Fiber.Fiber<void> | undefined;
expiresAt: number;
refCount: number;
}
const entry: State.Entry<A, E>const entry: {
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
finalizer: Effect.Effect<void>;
idleTimeToLive: Duration.Duration;
fiber: Fiber.Fiber<void> | undefined;
expiresAt: number;
refCount: number;
}
State<K, A, E>.Entry<A, E>.expiresAt: numberexpiresAt = clock: Clock(parameter) clock: {
currentTimeMillisUnsafe: () => number;
currentTimeMillis: Effect<number>;
currentTimeNanosUnsafe: () => bigint;
currentTimeNanos: Effect<bigint>;
sleep: (duration: Duration.Duration) => Effect<void>;
}
Clock.currentTimeMillisUnsafe(): numberReturns the current time in milliseconds unsafely.
When to use
Use to read millisecond time synchronously when you already have a Clock
service and can accept non-effectful access.
currentTimeMillisUnsafe() + import DurationDuration.const toMillis: (self: Input) => numberConverts a Duration to milliseconds.
Example (Converting durations to milliseconds)
import { Duration } from "effect"
console.log(Duration.toMillis(Duration.seconds(5))) // 5000
console.log(Duration.toMillis(Duration.minutes(2))) // 120000
toMillis(const entry: State.Entry<A, E>const entry: {
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
finalizer: Effect.Effect<void>;
idleTimeToLive: Duration.Duration;
fiber: Fiber.Fiber<void> | undefined;
expiresAt: number;
refCount: number;
}
State<K, A, E>.Entry<A, E>.idleTimeToLive: Duration.Duration(property) State<K, A, E>.Entry<A, E>.idleTimeToLive: {
value: DurationValue;
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;
}
import EffectEffect.const void: Effect.Effect<void, never, never>(alias) const void: {
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;
}
Returns an effect that succeeds with void.
void
})
)