input_file_generator.rb

MAIN_FUNC_STR = "x * x * Math.sin(x)"

def f(x)
  eval(MAIN_FUNC_STR)
end

File.open('input_file.txt', 'w') do |f|
  second_func_str = "f((x - 0.89) ** 1.12 - 0.35 * rand)"
  third_func_str = "f((0.89 * x) ** 0.89 + 0.1 * rand)"
  f << "x\t#{MAIN_FUNC_STR}\n"
  f << "#\tf(x)\t#{second_func_str}\t#{third_func_str}\n"
  3.step(21, 0.1) do |x|
    f << "%.1f\t%.3f\t%.3f\t%.3f\n" % [x * 2, f(x), eval(second_func_str), eval(third_func_str)]
  end
end