maclaurin.rb

class Maclaurin

  attr_reader :x, :steps, :function

  DERIVATIVE = {
    "sin" => "cos",
    "cos" => "-sin",
    "-sin" => "-cos",
    "-cos" => "sin",
    "e" => "e"
  }

  FUNCTION_VALUE = {
    "sin" => 0,
    "cos" => 1,
    "-cos" => -1,
    "-sin" => 0,
    "e" => 1
  }

  def initialize(function, x, steps)
    @x = x
    @steps = steps
    @function = function
  end

  def calculate
    series(function, 0, 0)
  end

  def series(function, step, number)
    return number if step > steps
    number += (x**step) * FUNCTION_VALUE[function] / factorial(step).to_f
    series(DERIVATIVE[function], step + 1, number)
  end

  def factorial(n)
    f = 1; for i in 1..n; f *= i; end; f
  end
end

# Przykladowe uzycie:

m1 =  Maclaurin.new("e", 1.2, 9)
puts "e^1.2 ~= #{m1.calculate}"

m2 =  Maclaurin.new("sin", 0.7, 5)
puts "sin(0.7) ~= #{m2.calculate}"

m3 =  Maclaurin.new("cos", 0.3, 6)
puts "cos(0.3) ~= #{m3.calculate}"