addHuman :: AgentId -> ZombiesPatch -> ZombiesPatch
addHuman aid (hs, z) = (aid : hs, z)
addHuman :: AgentId -> ZombiesPatch -> ZombiesPatch
addHuman aid (hs, z) = (aid : hs, z)
addHuman aid (hs, z) = (aid : hs, z)