Function _prod

src/compute-engine/interval/arithmetic.ts:81–84

* Endpoint product using the interval convention `0 · ±∞ = 0`. * * A plain `0 * Infinity` is `NaN`, which would poison `Math.min`/`Math.max` * and collapse the whole interval to `NaN` — e.g. `[0, 1] · [1, ∞)` or an * ordinary expression like `x · ln(x)` evaluated on `[0, 1]`. In interval * arit

(x: number, y: number)

 * arithmetic an exact zero endpoint annihilates an infinite one.
 */
function _prod(x: number, y: number): number {
  if (x === 0 || y === 0) return 0;
  return x * y;
}

/**
 * Multiply two intervals (or IntervalResults).