animator=klass()
function animator:init()
 self.operations={}
end
function animator:update()
 while true do
  if (#self.operations==0) return
  local op=self.operations[1]
  if op:update() then
   return true
  else
   deli(self.operations,1)
  end
 end
end
function animator:idle()
 return #self.operations==0
end
function animator:add(op)
 add(self.operations,op)
end
function animator:draw()
 for i=#self.operations,1,-1 do
  self.operations[i]:draw()
 end
end