load("./max.rb")
load("./abs.rb")

def draw_line(x0,y0,x1,y1,a)
  n=max(abs(x1-x0), abs(y1-y0))
  for i in 0..n
    x = x0+(x1-x0)*(i*1.0/n)
    y = y0+(y1-y0)*(i*1.0/n)
    if 0 <= y+0.5 && y+0.5 < a.   length() &&
       0 <= x+0.5 && x+0.5 < a[0].length()
      a[y+0.5][x+0.5]=1
    end
  end
end