RingLisp
https://github.com/zick/RingLisp
https://docs.google.com/presentation/d/1QCGnJk5FeI-1kdPB_g6xDd_DcqQxqGKOR8AbtKcXb8U/edit#slide=id.p
https://gyazo.com/ea56dfb1c7b61ee15ed3e39d8ba1a2cf
GCがない仕組み