Heroic Lands

Interface Rng

A seedable pseudo-random number generator. The core surface (float / uint32 / int / die) produces unbiased values; the control surface (seed / getState / setState) lets the singleton and e2e reset and snapshot the stream.

interface Rng {
    die(sides: number): number;
    float(): number;
    getState(): number[];
    int(min: number, max: number): number;
    seed(seed: string | number | number[]): void;
    setState(state: number[]): void;
    uint32(bound: number): number;
}

Implemented by

Methods

die float getState int seed setState uint32

Methods

die

  • die(sides: number): number

  • A uniform die roll in [1, sides].

    Parameters

    • sides: number

      Number of faces; must be >= 1.

    Returns number

    An integer 1 <= n <= sides.

    Throws

    If sides < 1.

float

  • float(): number

  • A uniform float in [0, 1) at 32-bit resolution (like Math.random).

    Returns number

    A pseudo-random number, 0 <= n < 1.

getState

  • getState(): number[]

  • Snapshot the internal state so it can be restored with setState (e2e captures before an action, replays after).

    Returns number[]

    A copy of the generator's state words — mutating it is safe.

int

  • int(min: number, max: number): number

  • A uniform integer in [min, max], inclusive on both ends.

    Parameters

    • min: number

      Inclusive lower bound.

    • max: number

      Inclusive upper bound; must be >= min.

    Returns number

    An integer min <= n <= max.

    Throws

    If max < min.

seed

  • seed(seed: string | number | number[]): void

  • Fully reset the stream to a known start (reset, not perturb). String seeds hash through cyrb128, so seeding each unit test with its own name gives an independent, reproducible stream for free.

    Parameters

    • seed: string | number | number[]

      A string, a single number, or the four state words directly.

    Returns void

setState

  • setState(state: number[]): void

  • Restore state previously produced by getState. Unlike seed, this sets the exact words with no re-mixing.

    Parameters

    • state: number[]

      The four state words to restore.

    Returns void

    Throws

    If state does not hold four words.

uint32

  • uint32(bound: number): number

  • A uniform integer in [0, bound), unbiased (rejection-sampled — no modulo/rounding skew, which matters on d100-scale hit-location tables).

    Parameters

    • bound: number

      Exclusive upper bound; must be >= 1.

    Returns number

    An integer 0 <= n < bound.

    Throws

    If bound < 1.

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