<A, E>(self: Dequeue<A, E>): Effect<A, E>Peeks at the next item without removing it.
Details
Blocks until an item is available. If the queue is done or fails, the error is propagated.
Example (Peeking at the next value)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(10)
yield* Queue.offer(queue, 42)
// Peek at the next item without removing it
const item = yield* Queue.peek(queue)
console.log(item) // 42
})taking
Source effect/Queue.ts:147110 lines
export const const peek: <A, E>(
self: Dequeue<A, E>
) => Effect<A, E>
Peeks at the next item without removing it.
Details
Blocks until an item is available. If the queue is done or fails, the error is propagated.
Example (Peeking at the next value)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(10)
yield* Queue.offer(queue, 42)
// Peek at the next item without removing it
const item = yield* Queue.peek(queue)
console.log(item) // 42
})
peek = <function (type parameter) A in <A, E>(self: Dequeue<A, E>): Effect<A, E>A, function (type parameter) E in <A, E>(self: Dequeue<A, E>): Effect<A, E>E>(self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) A in <A, E>(self: Dequeue<A, E>): Effect<A, E>A, function (type parameter) E in <A, E>(self: Dequeue<A, E>): Effect<A, E>E>): 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<function (type parameter) A in <A, E>(self: Dequeue<A, E>): Effect<A, E>A, function (type parameter) E in <A, E>(self: Dequeue<A, E>): Effect<A, E>E> =>
import internalEffectinternalEffect.const suspend: <A, E, R>(
evaluate: LazyArg<Effect.Effect<A, E, R>>
) => Effect.Effect<A, E, R>
self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.state: Queue.State<any, any>state._tag: "Open" | "Closing" | "Done"_tag === "Done") {
return self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.state: {
readonly _tag: "Done";
readonly exit: Failure<never, any>;
}
exit: Failure<never, E>(property) exit: {
_tag: "Failure";
cause: Cause.Cause<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; <…;
toString: () => string;
toJSON: () => unknown;
}
self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.messages: MutableList.MutableList<any>(property) Dequeue<out A, out E = never>.messages: {
head: MutableList.Bucket<A> | undefined;
tail: MutableList.Bucket<A> | undefined;
length: number;
}
MutableList<any>.length: numberlength > 0 && self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.messages: MutableList.MutableList<any>(property) Dequeue<out A, out E = never>.messages: {
head: MutableList.Bucket<A> | undefined;
tail: MutableList.Bucket<A> | undefined;
length: number;
}
MutableList<any>.head: MutableList.MutableList.Bucket<any> | undefinedhead) {
return import internalEffectinternalEffect.const succeed: <A>(
value: A
) => Effect.Effect<A>
self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.messages: MutableList.MutableList<any>(property) Dequeue<out A, out E = never>.messages: {
head: MutableList.Bucket<A> | undefined;
tail: MutableList.Bucket<A> | undefined;
length: number;
}
MutableList<any>.head: MutableList.MutableList.Bucket<any>(property) MutableList<any>.head: {
array: Array<A>;
mutable: boolean;
offset: number;
next: Bucket<A> | undefined;
}
MutableList<in out A>.Bucket<any>.array: any[]array[self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
Dequeue<out A, out E = never>.messages: MutableList.MutableList<any>(property) Dequeue<out A, out E = never>.messages: {
head: MutableList.Bucket<A> | undefined;
tail: MutableList.Bucket<A> | undefined;
length: number;
}
MutableList<any>.head: MutableList.MutableList.Bucket<any>(property) MutableList<any>.head: {
array: Array<A>;
mutable: boolean;
offset: number;
next: Bucket<A> | undefined;
}
MutableList<in out A>.Bucket<any>.offset: numberoffset])
}
return import internalEffectinternalEffect.const andThen: {
<A, B, E2, R2>(
f: (a: A) => Effect.Effect<B, E2, R2>
): <E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E | E2, R | R2>
<B, E2, R2>(f: Effect.Effect<B, E2, R2>): <
A,
E,
R
>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: (a: A) => Effect.Effect<B, E2, R2>
): Effect.Effect<B, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: Effect.Effect<B, E2, R2>
): Effect.Effect<B, E | E2, R | R2>
}
const awaitTake: <A, E>(
self: Dequeue<A, E>
) => Effect<void, E, never>
self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const peek: <A, E>(
self: Dequeue<A, E>
) => Effect<A, E>
Peeks at the next item without removing it.
Details
Blocks until an item is available. If the queue is done or fails, the error is propagated.
Example (Peeking at the next value)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(10)
yield* Queue.offer(queue, 42)
// Peek at the next item without removing it
const item = yield* Queue.peek(queue)
console.log(item) // 42
})
peek(self: Dequeue<A, E>(parameter) self: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}