<V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (
self: TxHashSet<V>
) => Effect.Effect<TxHashSet<U>>
<V>(predicate: Predicate<NoInfer<V>>): (
self: TxHashSet<V>
) => Effect.Effect<TxHashSet<V>>
<V, U extends V>(
self: TxHashSet<V>,
refinement: Refinement<V, U>
): Effect.Effect<TxHashSet<U>>
<V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<
TxHashSet<V>
>Filters the TxHashSet keeping only values that satisfy the predicate, returning a new TxHashSet.
Example (Filtering values)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
const numbers = yield* TxHashSet.make(1, 2, 3, 4, 5, 6)
const evens = yield* TxHashSet.filter(numbers, (n) => n % 2 === 0)
const values = yield* TxHashSet.toHashSet(evens)
console.log(Array.from(values).sort()) // [2, 4, 6]
console.log(yield* TxHashSet.size(evens)) // 3
})export const const filter: {
<V, U extends V>(
refinement: Refinement<NoInfer<V>, U>
): (
self: TxHashSet<V>
) => Effect.Effect<TxHashSet<U>>
<V>(predicate: Predicate<NoInfer<V>>): (
self: TxHashSet<V>
) => Effect.Effect<TxHashSet<V>>
<V, U extends V>(
self: TxHashSet<V>,
refinement: Refinement<V, U>
): Effect.Effect<TxHashSet<U>>
<V>(
self: TxHashSet<V>,
predicate: Predicate<V>
): Effect.Effect<TxHashSet<V>>
}
Filters the TxHashSet keeping only values that satisfy the predicate, returning a new TxHashSet.
Example (Filtering values)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
const numbers = yield* TxHashSet.make(1, 2, 3, 4, 5, 6)
const evens = yield* TxHashSet.filter(numbers, (n) => n % 2 === 0)
const values = yield* TxHashSet.toHashSet(evens)
console.log(Array.from(values).sort()) // [2, 4, 6]
console.log(yield* TxHashSet.size(evens)) // 3
})
filter: {
<function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U extends function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>(
refinement: Refinement<NoInfer<V>, U>refinement: interface Refinement<in A, out B extends A>A predicate that also narrows the input type when it returns true.
When to use
Use when you want a runtime check that refines A to B for TypeScript,
especially when composing type guards with
compose
or safely
checking unknown values.
Details
A refinement returns a type predicate (a is B). Use it with if or
filter to narrow types.
Example (Narrowing unknown values)
import { Predicate } from "effect"
const isString: Predicate.Refinement<unknown, string> = (u): u is string => typeof u === "string"
const data: unknown = "hello"
if (isString(data)) {
console.log(data.toUpperCase())
}
Type-level utilities for working with
Refinement
types.
When to use
Use when you need to extract input and output types from refinement
signatures while writing generic helpers over refinements.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting refinement types)
import { Predicate } from "effect"
type IsString = Predicate.Refinement<unknown, string>
type Input = Predicate.Refinement.In<IsString>
type Output = Predicate.Refinement.Out<IsString>
Refinement<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>, function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U>
): (self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>) => 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U>>
<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>(
predicate: Predicate<NoInfer<V>>predicate: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>>
): (self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>) => 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>>
<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U extends function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V>(
self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V>,
refinement: Refinement<V, U>refinement: interface Refinement<in A, out B extends A>A predicate that also narrows the input type when it returns true.
When to use
Use when you want a runtime check that refines A to B for TypeScript,
especially when composing type guards with
compose
or safely
checking unknown values.
Details
A refinement returns a type predicate (a is B). Use it with if or
filter to narrow types.
Example (Narrowing unknown values)
import { Predicate } from "effect"
const isString: Predicate.Refinement<unknown, string> = (u): u is string => typeof u === "string"
const data: unknown = "hello"
if (isString(data)) {
console.log(data.toUpperCase())
}
Type-level utilities for working with
Refinement
types.
When to use
Use when you need to extract input and output types from refinement
signatures while writing generic helpers over refinements.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting refinement types)
import { Predicate } from "effect"
type IsString = Predicate.Refinement<unknown, string>
type Input = Predicate.Refinement.In<IsString>
type Output = Predicate.Refinement.Out<IsString>
Refinement<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U>
): 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U>>
<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>(self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>, predicate: Predicate<V>predicate: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>): 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>>
} = dual<{
<V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>;
<V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>;
}, {
<V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>;
<V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>;
}>(arity: 2, body: {
<V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>;
<V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>;
}): {
<V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>;
<V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>;
} & {
<V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>;
<V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>;
} (+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) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U extends function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>(
refinement: Refinement<NoInfer<V>, U>refinement: interface Refinement<in A, out B extends A>A predicate that also narrows the input type when it returns true.
When to use
Use when you want a runtime check that refines A to B for TypeScript,
especially when composing type guards with
compose
or safely
checking unknown values.
Details
A refinement returns a type predicate (a is B). Use it with if or
filter to narrow types.
Example (Narrowing unknown values)
import { Predicate } from "effect"
const isString: Predicate.Refinement<unknown, string> = (u): u is string => typeof u === "string"
const data: unknown = "hello"
if (isString(data)) {
console.log(data.toUpperCase())
}
Type-level utilities for working with
Refinement
types.
When to use
Use when you need to extract input and output types from refinement
signatures while writing generic helpers over refinements.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting refinement types)
import { Predicate } from "effect"
type IsString = Predicate.Refinement<unknown, string>
type Input = Predicate.Refinement.In<IsString>
type Output = Predicate.Refinement.Out<IsString>
Refinement<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>, function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U>
): (self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>V>) => 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) U in <V, U extends V>(refinement: Refinement<NoInfer<V>, U>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<U>>U>>
<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>(
predicate: Predicate<NoInfer<V>>predicate: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>>
): (self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>) => 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(predicate: Predicate<NoInfer<V>>): (self: TxHashSet<V>) => Effect.Effect<TxHashSet<V>>V>>
},
{
<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U extends function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V>(
self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V>,
refinement: Refinement<V, U>refinement: interface Refinement<in A, out B extends A>A predicate that also narrows the input type when it returns true.
When to use
Use when you want a runtime check that refines A to B for TypeScript,
especially when composing type guards with
compose
or safely
checking unknown values.
Details
A refinement returns a type predicate (a is B). Use it with if or
filter to narrow types.
Example (Narrowing unknown values)
import { Predicate } from "effect"
const isString: Predicate.Refinement<unknown, string> = (u): u is string => typeof u === "string"
const data: unknown = "hello"
if (isString(data)) {
console.log(data.toUpperCase())
}
Type-level utilities for working with
Refinement
types.
When to use
Use when you need to extract input and output types from refinement
signatures while writing generic helpers over refinements.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting refinement types)
import { Predicate } from "effect"
type IsString = Predicate.Refinement<unknown, string>
type Input = Predicate.Refinement.In<IsString>
type Output = Predicate.Refinement.Out<IsString>
Refinement<function (type parameter) V in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>V, function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U>
): 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) U in <V, U extends V>(self: TxHashSet<V>, refinement: Refinement<V, U>): Effect.Effect<TxHashSet<U>>U>>
<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>(self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>, predicate: Predicate<V>predicate: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>): 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<interface TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>>V>>
}
>(2, <function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>, never, never>V>(self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashSet<in out V>A TxHashSet is a transactional hash set data structure that provides atomic operations on unique values within Effect transactions. It uses an immutable HashSet internally with TxRef for transactional semantics, ensuring all operations are performed atomically.
Details
Mutation operations such as add, remove, and clear update the original TxHashSet and return Effect<void> or Effect<boolean>. Transform operations such as union, intersection, difference, map, and filter create new TxHashSet instances and leave the original TxHashSet unchanged.
Example (Using transactional hash sets)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash set
const txSet = yield* TxHashSet.make("apple", "banana", "cherry")
// Single operations are automatically transactional
yield* TxHashSet.add(txSet, "grape")
const hasApple = yield* TxHashSet.has(txSet, "apple")
console.log(hasApple) // true
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const hasCherry = yield* TxHashSet.has(txSet, "cherry")
if (hasCherry) {
yield* TxHashSet.remove(txSet, "cherry")
yield* TxHashSet.add(txSet, "orange")
}
})
)
const size = yield* TxHashSet.size(txSet)
console.log(size) // 4
})
The TxHashSet namespace contains type-level utilities and helper types
for working with TxHashSet instances.
Example (Extracting value types inside transactions)
import { Effect, TxHashSet } from "effect"
const program = Effect.gen(function*() {
// Create a transactional color set
const colors = yield* TxHashSet.make("red", "green", "blue")
// Extract the value type for reuse
type Color = TxHashSet.TxHashSet.Value<typeof colors> // string
// Use extracted type in functions
const addColor = (color: Color) => TxHashSet.add(colors, color)
yield* addColor("yellow")
})
TxHashSet<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>, never, never>V>, predicate: Predicate<V>predicate: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<function (type parameter) V in <V>(self: TxHashSet<V>, predicate: Predicate<V>): Effect.Effect<TxHashSet<V>, never, never>V>) =>
import EffectEffect.const gen: {
<Eff extends Effect<any, any, any>, AEff>(
f: () => Generator<Eff, AEff, never>
): Effect<
AEff,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer E, infer _R>
]
? E
: never,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer _E, infer R>
]
? R
: never
>
<Self, Eff extends Effect<any, any, any>, AEff>(
options: { readonly self: Self },
f: (this: Self) => Generator<Eff, AEff, never>
): Effect<
AEff,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer E, infer _R>
]
? E
: never,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer _E, infer R>
]
? R
: never
>
}
const currentSet: HashSet.HashSet<V>const currentSet: {
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 TxRefTxRef.const get: <A>(
self: TxRef<A>
) => Effect.Effect<A>
Reads the current value of the TxRef.
When to use
Use to read the current value of a TxRef.
Example (Reading transactional references)
import { Effect, TxRef } from "effect"
const program = Effect.gen(function*() {
const counter = yield* TxRef.make(42)
// Read the value within a transaction
const value = yield* Effect.tx(
TxRef.get(counter)
)
console.log(value) // 42
})
get(self: TxHashSet<V>(parameter) self: {
ref: TxRef.TxRef<HashSet.HashSet<V>>;
toString: () => string;
toJSON: () => unknown;
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; <…;
}
TxHashSet<V>.ref: TxRef.TxRef<HashSet.HashSet<V>>(property) TxHashSet<V>.ref: {
version: number;
pending: Map<unknown, () => void>;
value: 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; <…;
}
const filteredSet: HashSet.HashSet<V>const filteredSet: {
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 HashSetHashSet.const filter: {
<V, U extends V>(
refinement: Refinement<NoInfer<V>, U>
): (self: HashSet<V>) => HashSet<U>
<V>(predicate: Predicate<NoInfer<V>>): (
self: HashSet<V>
) => HashSet<V>
<V, U extends V>(
self: HashSet<V>,
refinement: Refinement<V, U>
): HashSet<U>
<V>(
self: HashSet<V>,
predicate: Predicate<V>
): HashSet<V>
}
const currentSet: HashSet.HashSet<V>const currentSet: {
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;
}
predicate: Predicate<V>predicate)
return yield* const fromHashSet: <V>(
hashSet: HashSet.HashSet<V>
) => Effect.Effect<TxHashSet<V>>
Creates a TxHashSet from an existing HashSet.
Example (Creating a transactional hash set from a HashSet)
import { Effect, HashSet, TxHashSet } from "effect"
const program = Effect.gen(function*() {
const hashSet = HashSet.make("x", "y", "z")
const txSet = yield* TxHashSet.fromHashSet(hashSet)
console.log(yield* TxHashSet.size(txSet)) // 3
console.log(yield* TxHashSet.has(txSet, "y")) // true
// Original hashSet is unchanged when txSet is modified
yield* TxHashSet.add(txSet, "w")
console.log(HashSet.size(hashSet)) // 3 (original unchanged)
console.log(yield* TxHashSet.size(txSet)) // 4
})
fromHashSet(const filteredSet: HashSet.HashSet<V>const filteredSet: {
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;
}
Pipeable.pipe<Effect.Effect<TxHashSet<V>, never, never>, Effect.Effect<TxHashSet<V>, never, never>>(this: Effect.Effect<TxHashSet<V>, never, never>, ab: (_: Effect.Effect<TxHashSet<V>, never, never>) => Effect.Effect<TxHashSet<V>, never, never>): Effect.Effect<TxHashSet<V>, never, never> (+21 overloads)pipe(import EffectEffect.const tx: <A, E, R>(
effect: Effect<A, E, R>
) => Effect<A, E, Exclude<R, Transaction>>
Defines a transaction boundary. Transactions are "all or nothing" with respect to changes
made to transactional values (i.e. TxRef) that occur within the transaction body.
Details
If called inside an active transaction, tx composes with the current transaction and reuses
its journal and retry state instead of creating a nested boundary.
Effect transactions are optimistic with retry. A transaction is retried when
its body explicitly calls Effect.txRetry and any accessed transactional
value changes, or when any accessed transactional value changes because a
different transaction commits before the current one.
The outermost tx call creates the transaction boundary and commits or rolls back the full
composed transaction.
Example (Running a transaction)
import { Effect, TxRef } from "effect"
const program = Effect.gen(function*() {
const ref1 = yield* TxRef.make(0)
const ref2 = yield* TxRef.make(0)
// Nested tx calls compose into the same transaction
yield* Effect.tx(Effect.gen(function*() {
yield* TxRef.set(ref1, 10)
yield* Effect.tx(TxRef.set(ref2, 20))
const sum = (yield* TxRef.get(ref1)) + (yield* TxRef.get(ref2))
console.log(`Transaction sum: ${sum}`)
}))
console.log(`Final ref1: ${yield* TxRef.get(ref1)}`) // 10
console.log(`Final ref2: ${yield* TxRef.get(ref2)}`) // 20
})
tx))