code: func (d HypergeometicDist) PMF(k float64) float64 {
  	ki := int(math.Floor(k))
  	l, h := d.bounds()
  	if ki < l || ki > h {
  		return 0
  	}
  	return d.pmf(ki)
  }
docs: // PMF is the probability of getting exactly int(k) successes in
  // d.Draws draws with replacement from a population of size d.N that
  // contains exactly d.K successes.