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32 lines
1.2 KiB
JavaScript
32 lines
1.2 KiB
JavaScript
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/**
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* An implementation of the Lehmer / Parker-Miller linear congruential generator, a fast
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* pseudorandom number generator that can be seeded and of which multiple instances can be created.
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* (JavaScript's native random number generator cannot be seeded and is shared among everything
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* generating random numbers.)
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*/
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export class LcgRandom {
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// Constructs an instance with a given seed. Any integer can be input as the seed, however for
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// correct operation the seed used to initialize the state must be in the range [1, 2147483646],
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// so if the input seed is outside that range it is coerced into it.
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constructor(seed) {
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seed = seed % 2147483647;
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if (seed < 0) {
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seed *= -1;
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} else if (seed == 0) {
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seed = 1;
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}
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this._seed = seed;
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}
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// Returns an integer value in the range [min, max).
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getRandomInt(min, max) {
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return Math.floor(this.getRandomFloat() * (max - min)) + min;
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}
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// Returns a floating point value in the range [0, 1).
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getRandomFloat() {
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this._seed = this._seed * 48271 % 2147483647;
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return (this._seed - 1) / 2147483646;
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}
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} // class LcgRandom
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