小数点以下の桁数を取得

decimal_point.rb

def digits_after_decimal_point(val)
  return unless val.is_a?(Numeric)

  digits = 0
  while(val != val.to_i)
    digits += 1
    val *= 10
  end
  digits
end

sample

list = [1.0, 1.1, 1000000000.1, 1.0000000001]
#=> [1.0, 1.1, 1000000000.1, 1.0000000001]
list.map { |i| digits_after_decimal_point(i) }
#=> [0, 1, 1, 10]