@spissvinkel/alea/index.d.ts

Seedable PRNG for JS/TS

/**
 * An Alea PRNG
 */
export interface AleaPRNG {
    /**
     * @returns a pseudo-random floating-point number in the interval `[0, 1)` (like `Math.random()`)
     */
    random: () => number;
    /**
     * @returns a pseudo-random unsigned 32-bit integer in the interval `[0, 2^32)`
     */
    uint32: () => number;
    /**
     * @returns a pseudo-random full 53-bit fraction in the interval `[0, 1)`. (Slower than [[`AleaPRNG.random`]] but higher precision)
     */
    fract53: () => number;
    /**
     * Creates utility functions based on this PRNG, e.g.:
     * ```
     * const alea: AleaPRNG = mkAlea();
     * const nextBool: () => boolean = alea.nextT(n => n < 0.5);
     * // calling `nextBool()` now returns `true` or `false` at random
     * ```
     * @returns a function that, when invoked, transforms the next pseudo-random number `n` to a `T` using the provided function `f`
     */
    nextT: <T>(f: (n: number) => T) => () => T;
    /**
     * @returns a copy of the current state of this PRNG, which can be saved and then later passed to the [[`restoreAlea`]] function
     */
    getState: () => AleaState;
}
/**
 * The internal state of an Alea PRNG
 */
export interface AleaState {
    s0: number;
    s1: number;
    s2: number;
    c: number;
}
/**
 * Initialize a new PRNG
 *
 * @param seed an optional seed value
 * @returns an initialized PRNG
 */
export declare const mkAlea: (seed?: string) => AleaPRNG;
/**
 * Initialize a new PRNG from a previously saved state, effectively allowing the previous PRNG to be resumed
 *
 * @param state a state object, probably retrieved from an existing PRNG with [[`AleaPRNG.getState`]]
 * @returns an initialized PRNG
 */
export declare const restoreAlea: (state: AleaState) => AleaPRNG;
/**
 * @param state a state object, probably created with [[`mkState`]]. Will be updated as a side effect
 * @returns a pseudo-random floating-point number in the interval `[0, 1)` (like `Math.random()`)
 */
export declare const random: (state: AleaState) => number;
/**
 * @param state a state object, probably generated by [[`mkState`]]. Will be updated as a side effect
 * @returns a pseudo-random unsigned 32-bit integer in the interval `[0, 2^32)`
 */
export declare const uint32: (state: AleaState) => number;
/**
 * @param state a state object, probably generated with [[`mkState`]]. Will be updated as a side effect
 * @returns a pseudo-random full 53-bit fraction in the interval `[0, 1)`. (Slower than [[`random`]] but higher precision)
 */
export declare const fract53: (state: AleaState) => number;
/**
 * Creates utility functions based on the [[`random`]] function, e.g.:
 * ```
 * const state: AleaState = mkState('123');
 * const nextBool: (state: AleaState) => boolean = nextT(n => n < 0.5);
 * // calling `nextBool(state)` now returns `true` or `false` at random
 * ```
 * @param f a function to transform a number in the interval `[0, 1)` to a value of type `T`
 * @param state a state object, probably generated with [[`mkState`]]. Will be updated as a side effect
 * @returns a function that, when invoked with a state, transforms the next pseudo-random number `n` to a `T` using the provided function `f`
 */
export declare const nextT: <T>(f: (n: number) => T) => (state: AleaState) => T;
/**
 * Initializes a new PRNG state object using the provided seed value
 *
 * @param seed a seed value
 * @returns a new state object based on the provided `seed`
 */
export declare const mkState: (seed: string) => AleaState;
/**
 * Initializes a recycled PRNG state object using the provided seed value
 *
 * @param seed a seed value
 * @param state a state object to initialize
 * @returns the provided `state` object initialized using the provided `seed`
 */
export declare const initState: (seed: string, state: AleaState) => AleaState;
/**
 * Creates an uninitialized PRNG state object.
 * Must be initialized with [[`initState`]] before use
 *
 * @returns a new, uninitialized state object
 */
export declare const emptyState: () => AleaState;
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