信息素的产生结束其变异2

Question

这是我们的程序，但我们有一个问题，信息素永远不会是0，我们需要它为0 应该做什么？

LayPheromone

     if (pheromone < maxPheroPerSite-Forage)

        [set pheromone (pheromone + amtPheroLay-Forage)]

    end    
   to UpdatePatches
  ask patch nestX nestY [ set pcolor pink ]
 ask patches

[

if (pheromone < 0) [set pheromone 0]

if (pheromone > 0)

    [

    set pheromone (pheromone - pheromone * evaporation-rate)

    ifelse showPhero?
      [ set pcolor scale-color yellow pheromone 0 (maxPheroPerSite-Forage)]

      [ set pcolor black ]
    ]
] `