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149839b60c
Co-authored-by: Yoshiya Hinosawa <stibium121@gmail.com> Co-authored-by: Asher Gomez <ashersaupingomez@gmail.com>
42 lines
1.4 KiB
TypeScript
42 lines
1.4 KiB
TypeScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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// This module is browser compatible.
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import { fromSeed, nextU32, seedFromU64 } from "./_pcg32.ts";
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import type { Prng } from "./_types.ts";
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/**
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* Creates a pseudo-random number generator that generates random numbers in
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* the range `[0, 1)`, based on the given seed. The algorithm used for
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* generation is {@link https://www.pcg-random.org/download.html | PCG32}.
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*
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* @experimental **UNSTABLE**: New API, yet to be vetted.
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*
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* @param seed The seed used to initialize the random number generator's state.
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* @returns A pseudo-random number generator function, which will generate
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* different random numbers on each call.
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*
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* @example Usage
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* ```ts
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* import { randomSeeded } from "@std/random";
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* import { assertEquals } from "@std/assert";
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*
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* const prng = randomSeeded(1n);
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*
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* assertEquals(prng(), 0.20176767697557807);
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* assertEquals(prng(), 0.4911644416861236);
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* assertEquals(prng(), 0.7924694607499987);
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* ```
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*/
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export function randomSeeded(seed: bigint): Prng {
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const pcg = fromSeed(seedFromU64(seed, 16));
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return () => uint32ToFloat64(nextU32(pcg));
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}
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/**
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* Convert a 32-bit unsigned integer to a float64 in the range `[0, 1)`.
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* This operation is lossless, i.e. it's always possible to get the original
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* value back by multiplying by 2 ** 32.
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*/
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function uint32ToFloat64(u32: number): number {
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return u32 / 2 ** 32;
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}
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