export Random.make taking hashable values as seed (#3203)

.changeset/rich-insects-jog.md

@@ -0,0 +1,5 @@
+---
+"effect": minor
+---
+
+export Random.make taking hashable values as seed

packages/effect/src/Random.ts

@@ -118,3 +118,12 @@ export const randomWith: <A, E, R>(f: (random: Random) => Effect.Effect<A, E, R>
  * @category context
  */
 export const Random: Context.Tag<Random, Random> = internal.randomTag
+
+/**
+ * Constructs the `Random` service, seeding the pseudo-random number generator
+ * with an hash of the specified seed.
+ *
+ * @since 3.5.0
+ * @category constructors
+ */
+export const make: <A>(seed: A) => Random = internal.make

packages/effect/src/internal/defaultServices.ts

@@ -22,7 +22,7 @@ export const liveServices: Context.Context<DefaultServices.DefaultServices> = pi
   Context.empty(),
   Context.add(clock.clockTag, clock.make()),
   Context.add(console_.consoleTag, console_.defaultConsole),
-  Context.add(random.randomTag, random.make((Math.random() * 4294967296) >>> 0)),
+  Context.add(random.randomTag, random.make(Math.random())),
   Context.add(configProvider.configProviderTag, configProvider.fromEnv()),
   Context.add(tracer.tracerTag, tracer.nativeTracer)
 )

packages/effect/src/internal/random.ts

@@ -2,6 +2,7 @@ import * as Chunk from "../Chunk.js"
 import * as Context from "../Context.js"
 import type * as Effect from "../Effect.js"
 import { pipe } from "../Function.js"
+import * as Hash from "../Hash.js"
 import type * as Random from "../Random.js"
 import * as PCGRandom from "../Utils.js"
 import * as core from "./core.js"
@@ -85,4 +86,4 @@ const swap = <A>(buffer: Array<A>, index1: number, index2: number): Array<A> =>
   return buffer
 }
 
-export const make = (seed: number): Random.Random => new RandomImpl(seed)
+export const make = <A>(seed: A): Random.Random => new RandomImpl(Hash.hash(seed))

packages/effect/test/Random.test.ts

@@ -1,4 +1,4 @@
-import { Array, Chunk, Effect, Random } from "effect"
+import { Array, Chunk, Data, Effect, Random } from "effect"
 import * as it from "effect/test/utils/extend"
 import { assert, describe } from "vitest"
 
@@ -10,4 +10,19 @@ describe("Random", () => {
       assert.isTrue(Chunk.every(end, (n) => n !== undefined))
       assert.deepStrictEqual(start.sort(), Array.fromIterable(end).sort())
     }).pipe(Effect.repeatN(100)))
+
+  it.effect("make", () =>
+    Effect.gen(function*() {
+      const random0 = Random.make("foo")
+      const random1 = Random.make("foo")
+      const random2 = Random.make(Data.struct({ foo: "bar" }))
+      const random3 = Random.make(Data.struct({ foo: "bar" }))
+      const n0 = yield* random0.next
+      const n1 = yield* random1.next
+      const n2 = yield* random2.next
+      const n3 = yield* random3.next
+      assert.strictEqual(n0, n1)
+      assert.strictEqual(n2, n3)
+      assert.notStrictEqual(n0, n2)
+    }))
 })