(seed: string | number): <A, E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A, E, R>
<A, E, R>(
self: Effect.Effect<A, E, R>,
seed: string | number
): Effect.Effect<A, E, R>Seeds the pseudo-random number generator with the specified value.
When to use
Use to run an effect with a deterministic pseudo-random sequence.
Details
Using the same seed produces the same random sequence, which is useful for tests and reproducible simulations.
Gotchas
Use an unpredictable seed when uniqueness or unpredictability matters.
Example (Seeding random generation)
import { Effect, Random } from "effect"
const program = Effect.gen(function*() {
const value1 = yield* Random.next
const value2 = yield* Random.next
console.log(value1, value2)
})
// Same seed produces same sequence
const seeded1 = program.pipe(Random.withSeed("my-seed"))
const seeded2 = program.pipe(Random.withSeed("my-seed"))
// Both will output identical values
Effect.runPromise(seeded1)
Effect.runPromise(seeded2)Seeding
Source effect/Random.ts:3097 lines
export const const withSeed: {
(seed: string | number): <A, E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A, E, R>
<A, E, R>(
self: Effect.Effect<A, E, R>,
seed: string | number
): Effect.Effect<A, E, R>
}
Seeds the pseudo-random number generator with the specified value.
When to use
Use to run an effect with a deterministic pseudo-random sequence.
Details
Using the same seed produces the same random sequence, which is useful for
tests and reproducible simulations.
Gotchas
Use an unpredictable seed when uniqueness or unpredictability matters.
Example (Seeding random generation)
import { Effect, Random } from "effect"
const program = Effect.gen(function*() {
const value1 = yield* Random.next
const value2 = yield* Random.next
console.log(value1, value2)
})
// Same seed produces same sequence
const seeded1 = program.pipe(Random.withSeed("my-seed"))
const seeded2 = program.pipe(Random.withSeed("my-seed"))
// Both will output identical values
Effect.runPromise(seeded1)
Effect.runPromise(seeded2)
withSeed: {
(seed: string | numberseed: string | number): <function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>R>(self: Effect.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;
}
import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>R>) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>R>
<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>R>(self: Effect.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;
}
import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>R>, seed: string | numberseed: string | number): import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>A, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>E, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): Effect.Effect<A, E, R>R>
} = import dualdual(2, <function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyA, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyE, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyR>(
self: Effect.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;
}
import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) A in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyA, function (type parameter) E in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyE, function (type parameter) R in <A, E, R>(self: Effect.Effect<A, E, R>, seed: string | number): anyR>,
seed: string | numberseed: string | number
) => import EffectEffect.provideService(self: Effect.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;
}
const Random: Context.Reference<{
nextIntUnsafe(): number
nextDoubleUnsafe(): number
}>
const Random: {
key: string;
Service: {
nextIntUnsafe: () => number;
nextDoubleUnsafe: () => number;
};
defaultValue: () => Shape;
of: (this: void, self: { nextIntUnsafe(): number; nextDoubleUnsafe(): number }) => { nextIntUnsafe(): number; nextDoubleUnsafe(): number };
context: (self: { nextIntUnsafe(): number; nextDoubleUnsafe(): number }) => Context.Context<never>;
use: (f: (service: { nextIntUnsafe(): number; nextDoubleUnsafe(): number }) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
useSync: (f: (service: { nextIntUnsafe(): number; nextDoubleUnsafe(): number }) => A) => Effect.Effect<A, never, never>;
Identifier: Identifier;
stack: string | 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; <…;
toString: () => string;
toJSON: () => unknown;
}
Represents a service for generating pseudo-random numbers.
When to use
Use to access or provide the random-number generator service used by Effect
programs.
Gotchas
The default implementation is based on Math.random and is not
cryptographically secure. Replace the service with a cryptographically secure
implementation before using these generators for security-sensitive values.
Example (Accessing the random service)
import { Effect, Random } from "effect"
const program = Effect.gen(function*() {
const float = yield* Random.next
const integer = yield* Random.nextInt
const inRange = yield* Random.nextIntBetween(1, 100)
console.log("Float:", float)
console.log("Integer:", integer)
console.log("In range:", inRange)
})
Random, function ISAAC_CSPRNG(
userSeed?: string | number
): {
nextIntUnsafe: () => number
nextDoubleUnsafe: () => number
}
seed: string | numberseed)))