mysticsymbolic.github.io/lib/random.ts

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TypeScript
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2021-02-15 13:34:05 +00:00
export type RandomParameters = {
modulus: number;
multiplier: number;
increment: number;
};
const NUMERICAL_RECIPES_PARAMETERS: RandomParameters = {
modulus: Math.pow(2, 32),
multiplier: 1664525,
increment: 1013904223,
};
/**
* A simple linear congruential random number generator, as described in
* https://en.wikipedia.org/wiki/Linear_congruential_generator.
*/
export class Random {
private latestSeed: number;
constructor(
readonly seed: number = Date.now(),
readonly params: RandomParameters = NUMERICAL_RECIPES_PARAMETERS
) {
this.latestSeed = seed;
}
/**
* Return a random number that is greater than or equal to zero, and less
* than one.
*/
next(): number {
this.latestSeed =
(this.params.multiplier * this.latestSeed + this.params.increment) %
this.params.modulus;
return this.latestSeed / this.params.modulus;
}
/**
* Return a random item from the given array.
*/
choice<T>(array: T[]): T {
const idx = Math.floor(this.next() * array.length);
return array[idx];
}
}