function minusOneUlp(value) {
        if (value === 0) throw new Error(`yeah, can't do that`);
        const f64 = new Float64Array([value]);
        const big64 = new BigInt64Array(f64.buffer);
        big64[0] -= 1n;
        return f64[0];
      }
Returns the next smaller representable double value.
@type {number} value