code: func (ung UniformGenerator) Float64Range(a, b float64) float64 {
  	if !(a < b) {
  		panic(fmt.Sprintf("Invalid range: %.2f ~ %.2f", a, b))
  	}
  	return a + ung.Float64()*(b-a)
  }
docs: // Float32Range returns a random float32 in [a, b)