<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>Invalidates and removes a specific key from the RcMap. If the resource is not currently in use (reference count is 0), it will be immediately released.
When to use
Use to remove a resource by key so the next access performs a fresh lookup.
Example (Invalidating a resource)
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}`)
)
})
// Get a resource
yield* RcMap.get(map, "cache")
// Invalidate the resource - it will be removed from the map
// and released if no longer in use
yield* RcMap.invalidate(map, "cache")
// Next access will create a new resource
yield* RcMap.get(map, "cache")
}).pipe(Effect.scoped)export const const invalidate: {
<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>
}
Invalidates and removes a specific key from the RcMap. If the resource is not
currently in use (reference count is 0), it will be immediately released.
When to use
Use to remove a resource by key so the next access performs a fresh lookup.
Example (Invalidating a resource)
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}`)
)
})
// Get a resource
yield* RcMap.get(map, "cache")
// Invalidate the resource - it will be removed from the map
// and released if no longer in use
yield* RcMap.invalidate(map, "cache")
// Next access will create a new resource
yield* RcMap.get(map, "cache")
}).pipe(Effect.scoped)
invalidate: {
<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,
import EffectEffect.const fnUntraced: <Effect.Effect<void, never, never>, void, [self: RcMap<K, A, E>, key: K], Effect.Effect<void, never, never>>(body: (this: unassigned, self: RcMap<K, A, E>, key: K) => Generator<Effect.Effect<void, never, never>, void, never>, a: (_: Effect.Effect<void, never, never>, self: RcMap<K, A, E>, key: K) => Effect.Effect<void, never, never>) => <K, A, E>(self: RcMap<K, A, E>, key: K) => Effect.Effect<void, never, never> (+41 overloads)fnUntraced(function*<function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>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): Generator<Effect.Effect<void, never, never>, void, any>K, function (type parameter) A in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>A, function (type parameter) E in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>E>, key: Kkey: function (type parameter) K in <K, A, E>(self: RcMap<K, A, E>, key: K): Generator<Effect.Effect<void, never, never>, void, any>K) {
if (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
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") return
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;
}
import MutableHashMapMutableHashMap.const remove: {
<K>(key: K): <V>(
self: MutableHashMap<K, V>
) => MutableHashMap<K, V>
<K, V>(
self: MutableHashMap<K, V>,
key: K
): MutableHashMap<K, 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 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>.refCount: numberrefCount > 0) return
if (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>.fiber: Fiber.Fiber<void> | undefinedfiber) yield* import FiberFiber.const interrupt: <A, E>(
self: Fiber<A, E>
) => Effect<void>
Interrupts a fiber, causing it to stop executing and clean up any
acquired resources.
When to use
Use when you need to cancel a forked fiber and wait for its cleanup to
complete.
Details
The returned Effect completes only after the interrupted fiber has completed.
Gotchas
Interruption is cooperative. A fiber can continue running while it is inside
uninterruptible work or finalizers.
Example (Interrupting a fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
const fiber = yield* Effect.forkChild(
Effect.delay("1 second")(Effect.succeed(42))
)
yield* Fiber.interrupt(fiber)
console.log("Fiber interrupted")
})
interrupt(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>.fiber: Fiber.Fiber<void> | undefined(property) State<K, A, E>.Entry<A, E>.fiber: {
id: number;
currentOpCount: number;
getRef: <A>(ref: Context.Reference<A>) => A;
context: Context.Context<never>;
setContext: (context: Context.Context<never>) => void;
currentScheduler: Scheduler;
currentDispatcher: SchedulerDispatcher;
currentSpan: AnySpan | undefined;
currentLogLevel: LogLevel;
minimumLogLevel: LogLevel;
currentStackFrame: StackFrame | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
addObserver: (cb: (exit: Exit<A, E>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit<A, E> | undefined;
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; <…;
}
import ScopeScope.const close: <A, E>(
self: Scope,
exit: Exit<A, E>
) => Effect<void>
Closes a scope and runs its registered finalizers.
When to use
Use to close a scope manually with a specific exit value.
Details
Finalizers run in the scope's configured order and receive the supplied
Exit.
Example (Running scope finalizers)
import { Console, Effect, Exit, Scope } from "effect"
const resourceManagement = Effect.gen(function*() {
const scope = yield* Scope.make("sequential")
// Add multiple finalizers
yield* Scope.addFinalizer(scope, Console.log("Close database connection"))
yield* Scope.addFinalizer(scope, Console.log("Close file handle"))
yield* Scope.addFinalizer(scope, Console.log("Release memory"))
// Do some work...
yield* Console.log("Performing operations...")
// Close scope - finalizers run in reverse order of registration
yield* Scope.close(scope, Exit.succeed("Success!"))
// Output: "Release memory", "Close file handle", "Close database connection"
})
close(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>.scope: Scope.Closeable(property) State<K, A, E>.Entry<A, E>.scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import ExitExit.const void: Exit.Exit<void, never>Provides a pre-allocated successful Exit with a void value.
When to use
Use when you need a shared successful Exit with no meaningful value.
Details
Equivalent to Exit.succeed(undefined) but shared as a single instance,
avoiding allocation for a common case.
Example (Referencing the void Exit)
import { Exit } from "effect"
const exit = Exit.void
console.log(Exit.isSuccess(exit)) // true
void)
}, import EffectEffect.const uninterruptible: <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E, R>
Returns a new effect that disables interruption for the given effect.
Example (Preventing interruption)
import { Console, Effect, Fiber } from "effect"
const criticalTask = Effect.gen(function*() {
yield* Console.log("Starting critical section...")
yield* Effect.sleep("2 seconds")
yield* Console.log("Critical section completed")
})
const program = Effect.uninterruptible(criticalTask)
const fiber = Effect.runFork(program)
// Even if interrupted, the critical task will complete
Effect.runPromise(Fiber.interrupt(fiber))
uninterruptible)
)