def scaled_digit(group)
      unless group.size == @base_scale
        raise "Invalid digits group size for scaled_digit (is #{group.size}; should be #{@base_scale})"
      end
      v = 0
      group.each do |digit|
        v *= @setter.base
        v += digit
      end
      v
    end
def scaled_digit(group)
      unless group.size == @base_scale
        raise "Invalid digits group size for scaled_digit (is #{group.size}; should be #{@base_scale})"
      end
      v = 0
      group.each do |digit|
        v *= @setter.base
        v += digit
      end
      v
    end
Return the `scaled_base` digit corresponding to a group of `base_scale` `exponent_base` digits