#!/usr/bin/ruby


def birth
  dice = rand(100)
  return dice > 50 ? 1 : 0
end


### 生了男孩就不生了，生了女孩就一直生
def family_birth(kids=[])
  kid = birth
  kids.push(kid)
  return kids if kid == 1
  family_birth(kids) if kid == 0
end

### 家里只准生两个女孩，第三胎是女孩就打掉，是男孩就生
def family_birth_type2(kids=[])
  kid = birth
  if kid == 1
    kids.push(kid)
    return kids
  elsif kid == 0 and kids.empty?
    kids.push(kid)
    family_birth_type2(kids)
  elsif kid == 0 and kids == [0]
    kids.push(kid)
    family_birth_type2(kids)
  elsif kid == 0 and kids == [0,0]
    family_birth_type2(kids)
  end
end

def bias(n)
  kids = []
  1.upto(n) do |i|
    family_children = family_birth
    kids.push(family_children)
  end
  return [kids.flatten.count(1),kids.flatten.count(0)]
end

def bias_type2(n)
  kids = []
  1.upto(n) do |i|
	family_children = family_birth_type2
	kids.push(family_children)
  end
  return [kids.flatten.count(1),kids.flatten.count(0)]
end

def flat(n)
  kids = []
  1.upto(n) do |i|
    kids.push(birth)
  end
  return [kids.count(1),kids.count(0)]
end

def plot(start,step,count,func)
  i = 0
  while i < count - 1
    kids = Object.send(func,start + i * step)
    p kids[0]/kids[1].to_f
    i = i + step
  end
end

plot(10000,100,50000,'bias_type2')