class RandomBell

# File lib/random_bell.rb, line 9
def initialize(mu: 0.5, sigma: 0.2, range: 0.0..1.0, seed: Random.new_seed, method: :box_muller)
  @mu     = mu
  @sigma  = sigma
  @range  = range
  @rand_generator = Random.new(seed)
  @method = method
end

# File lib/random_bell.rb, line 23
def normal
  @mu + standard * @sigma
end

# File lib/random_bell.rb, line 28
def rand
  loop do
    num = normal
    return num if @range.include?(num)
  end
end

# File lib/random_bell.rb, line 18
def standard
  send(@method)
end

# File lib/random_bell.rb, line 36
def to_histogram(rows: 20, size: 10 ** 4)
  histogram = ""

  numbers = (1..size).to_a.map{ rand }

  klasses, klass_width = [], (@range.max - @range.min).to_f / rows
  (0..rows).each_cons(2) do |left, right|
    klasses << Range.new(@range.min + klass_width * left, @range.min + klass_width * right)
  end

  divider = (klasses.map{|klass| numbers.select{|num| klass.include?(num) }.size }.max / 50.0).ceil
  klasses.each do |klass|
    n = numbers.select{|num| klass.include?(num) }.size / divider
    histogram << sprintf("%+3.3f", klass.max) << ": " << "*" * n << "\n"
  end

  histogram
end

# File lib/random_bell.rb, line 58
def box_muller
  @box_muller_queue ||= []

  if @box_muller_queue.empty?
    theta  = 2 * Math::PI * random_number
    r      = Math.sqrt( -2 * Math.log(random_number) )
    z1, z2 = r * Math.cos(theta), r * Math.sin(theta)
    @box_muller_queue += [z1, z2]
  end

  @box_muller_queue.shift
end

# File lib/random_bell.rb, line 72
def central_limit
  arr = []
  12.times{ arr << random_number }
  arr.reduce(0.0, &:+) - 6
end

# File lib/random_bell.rb, line 79
def random_number
  @rand_generator.rand
end