46 wiersze
1.0 KiB
TypeScript
46 wiersze
1.0 KiB
TypeScript
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export type RandomParameters = {
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modulus: number;
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multiplier: number;
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increment: number;
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};
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const NUMERICAL_RECIPES_PARAMETERS: RandomParameters = {
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modulus: Math.pow(2, 32),
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multiplier: 1664525,
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increment: 1013904223,
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};
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/**
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* A simple linear congruential random number generator, as described in
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* https://en.wikipedia.org/wiki/Linear_congruential_generator.
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*/
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export class Random {
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private latestSeed: number;
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constructor(
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readonly seed: number = Date.now(),
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readonly params: RandomParameters = NUMERICAL_RECIPES_PARAMETERS
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) {
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this.latestSeed = seed;
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}
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/**
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* Return a random number that is greater than or equal to zero, and less
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* than one.
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*/
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next(): number {
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this.latestSeed =
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(this.params.multiplier * this.latestSeed + this.params.increment) %
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this.params.modulus;
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return this.latestSeed / this.params.modulus;
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}
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/**
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* Return a random item from the given array.
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*/
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choice<T>(array: T[]): T {
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const idx = Math.floor(this.next() * array.length);
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return array[idx];
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}
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}
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