<A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>
<A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>Applies map eagerly when an effect is already resolved.
When to use
Use when an already-resolved effect should apply a success transformation immediately while pending effects still use regular mapping.
Details
Success effects apply the mapping function immediately. Failure effects pass
through unchanged, and pending effects fall back to regular map behavior.
Example (Mapping already completed effects)
import { Effect } from "effect"
// For resolved effects, the mapping is applied immediately
const resolved = Effect.succeed(5)
const mapped = Effect.mapEager(resolved, (n) => n * 2) // Applied eagerly
// For pending effects, behaves like regular map
const pending = Effect.delay(Effect.succeed(5), "100 millis")
const mappedPending = Effect.mapEager(pending, (n) => n * 2) // Uses regular mapexport const const mapEager: {
<A, B>(f: (a: A) => B): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
f: (a: A) => B
): Effect<B, E, R>
}
Applies map eagerly when an effect is already resolved.
When to use
Use when an already-resolved effect should apply a success transformation
immediately while pending effects still use regular mapping.
Details
Success effects apply the mapping function immediately. Failure effects pass
through unchanged, and pending effects fall back to regular map behavior.
Example (Mapping already completed effects)
import { Effect } from "effect"
// For resolved effects, the mapping is applied immediately
const resolved = Effect.succeed(5)
const mapped = Effect.mapEager(resolved, (n) => n * 2) // Applied eagerly
// For pending effects, behaves like regular map
const pending = Effect.delay(Effect.succeed(5), "100 millis")
const mappedPending = Effect.mapEager(pending, (n) => n * 2) // Uses regular map
mapEager: {
<function (type parameter) A in <A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>A, function (type parameter) B in <A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>B>(f: (a: A) => Bf: (a: Aa: function (type parameter) A in <A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>A) => function (type parameter) B in <A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>B): <function (type parameter) E in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>E, function (type parameter) R in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>R>(self: Effect<A, E, R>(parameter) self: {
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;
}
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, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>A, function (type parameter) E in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>E, function (type parameter) R in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>R>) => 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) B in <A, B>(f: (a: A) => B): <E, R>(self: Effect<A, E, R>) => Effect<B, E, R>B, function (type parameter) E in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>E, function (type parameter) R in <E, R>(self: Effect<A, E, R>): Effect<B, E, R>R>
<function (type parameter) A in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>R, function (type parameter) B in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>B>(self: Effect<A, E, R>(parameter) self: {
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;
}
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, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>R>, f: (a: A) => Bf: (a: Aa: function (type parameter) A in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>A) => function (type parameter) B in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>B): 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) B in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>B, function (type parameter) E in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Effect<A, E, R>, f: (a: A) => B): Effect<B, E, R>R>
} = import internalinternal.const mapEager: {
<A, B>(f: (a: A) => B): <E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E, R>
<A, E, R, B>(
self: Effect.Effect<A, E, R>,
f: (a: A) => B
): Effect.Effect<B, E, R>
}